diff --git a/backend/src/main/java/org/sejongisc/backend/activity/repository/ActivityLogRepository.java b/backend/src/main/java/org/sejongisc/backend/activity/repository/ActivityLogRepository.java
index cf2de3fb..ac1326aa 100644
--- a/backend/src/main/java/org/sejongisc/backend/activity/repository/ActivityLogRepository.java
+++ b/backend/src/main/java/org/sejongisc/backend/activity/repository/ActivityLogRepository.java
@@ -2,6 +2,7 @@
 
 import org.sejongisc.backend.activity.entity.ActivityLog;
 import org.sejongisc.backend.activity.entity.ActivityType;
+import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Slice;
 import org.springframework.data.jpa.repository.JpaRepository;
@@ -15,9 +16,8 @@
 public interface ActivityLogRepository extends JpaRepository<ActivityLog, Long> {
     // 마이페이지 내 활동 조회
     @Query("SELECT a FROM ActivityLog a WHERE a.userId = :userId " +
-            "AND a.activityType IN :activityTypes " +
-            "ORDER BY a.createdAt DESC")
-    List<ActivityLog> findByUserIdAndActivityTypesOrderByCreatedAtDesc(UUID userId, List<ActivityType> activityTypes);
+        "AND a.activityType IN :activityTypes")
+    Page<ActivityLog> findByUserIdAndActivityTypeIn(@Param("userId") UUID userId, @Param("activityTypes") List<ActivityType> activityTypes, Pageable pageable);
 
     @Query("SELECT COUNT(a) FROM ActivityLog a " +
         "WHERE a.activityType IN :types " +
diff --git a/backend/src/main/java/org/sejongisc/backend/admin/controller/AdminUserController.java b/backend/src/main/java/org/sejongisc/backend/admin/controller/AdminUserController.java
index c7a725cd..3db8c3eb 100644
--- a/backend/src/main/java/org/sejongisc/backend/admin/controller/AdminUserController.java
+++ b/backend/src/main/java/org/sejongisc/backend/admin/controller/AdminUserController.java
@@ -7,6 +7,7 @@
 import org.sejongisc.backend.admin.dto.AdminUserResponse;
 import org.sejongisc.backend.admin.dto.ExcelSyncResponse;
 import org.sejongisc.backend.admin.service.AdminUserService;
+import org.sejongisc.backend.user.entity.Grade;
 import org.sejongisc.backend.user.entity.Role;
 import org.sejongisc.backend.user.entity.UserStatus;
 import org.springframework.http.MediaType;
@@ -60,9 +61,9 @@ public ResponseEntity<List<AdminUserResponse>> getAllUsers(@ModelAttribute Admin
         return ResponseEntity.ok(adminUserService.findAllUsers(request));
     }
 
-    @Operation(summary = "회원 활동 상태 변경", description = "ACTIVE, INACTIVE, GRADUATED 등으로 상태를 변경합니다. (시스템 관리자용)")
+    @Operation(summary = "회원 활동 상태 변경", description = "ACTIVE, INACTIVE, OUT으로 상태를 변경합니다. (시스템 관리자용)")
     @PatchMapping("/{userId}/status")
-    @PreAuthorize("hasAnyRole('SYSTEM_ADMIN')")
+    @PreAuthorize("hasAnyRole('PRESIDENT', 'SYSTEM_ADMIN')")
     public ResponseEntity<?> updateUserStatus(
             @PathVariable UUID userId,
             @RequestParam UserStatus status) {
@@ -74,7 +75,7 @@ public ResponseEntity<?> updateUserStatus(
     // TODO : 회장 권한 논의 필요
     @Operation(summary = "회원 권한 변경", description = "특정 유저의 Role(PRESIDENT, VICE_PRESIDENT, TEAM_LEADER)을 변경합니다. (시스템 관리자용)")
     @PatchMapping("/{userId}/role")
-    @PreAuthorize("hasRole('SYSTEM_ADMIN')")
+    @PreAuthorize("hasAnyRole('PRESIDENT', 'SYSTEM_ADMIN')")
     public ResponseEntity<?> updateUserRole(
             @PathVariable UUID userId,
             @RequestParam Role role) {
@@ -82,17 +83,28 @@ public ResponseEntity<?> updateUserRole(
         return ResponseEntity.noContent().build();
     }
 
-    @Operation(summary = "선배(SENIOR) 등급 변경", description = "특정 유저를 선배(SENIOR) 등급으로 변경합니다. (회장/관리자용)")
-    @PatchMapping("/{userId}/senior")
+    @Operation(summary = "회원 신분 변경", description = """
+        특정 유저의 신분(GRADE)을 변경합니다. (회장/관리자용)
+        
+        ## 요청방식
+        ?grade=NEW_MEMBER
+        
+        ## 종류
+        - NEW_MEMBER, // 신입부원
+        - ASSOCIATE_MEMBER, // 준회원
+        - REGULAR_MEMBER, // 정회원
+    """)
+    @PatchMapping("/{userId}/grade")
     @PreAuthorize("hasAnyRole('PRESIDENT', 'SYSTEM_ADMIN')")
-    public ResponseEntity<Void> promoteToSenior(@PathVariable UUID userId) {
-        adminUserService.promoteToSenior(userId);
+    public ResponseEntity<Void> promoteToSenior(@PathVariable UUID userId,
+                                                @RequestParam Grade grade) {
+        adminUserService.updateUserGrade(userId, grade);
         return ResponseEntity.noContent().build();
     }
 
     @Operation(summary = "회원 강제 탈퇴", description = "시스템에서 유저를 탈퇴 처리합니다. (시스템 관리자용)")
     @DeleteMapping("/{userId}")
-    @PreAuthorize("hasRole('SYSTEM_ADMIN')")
+    @PreAuthorize("hasAnyRole('PRESIDENT', 'SYSTEM_ADMIN')")
     public ResponseEntity<?> forceDeleteUser(@PathVariable UUID userId) {
         adminUserService.deleteUser(userId);
         return ResponseEntity.noContent().build();
diff --git a/backend/src/main/java/org/sejongisc/backend/admin/service/AdminUserService.java b/backend/src/main/java/org/sejongisc/backend/admin/service/AdminUserService.java
index b0287d45..68e1444e 100644
--- a/backend/src/main/java/org/sejongisc/backend/admin/service/AdminUserService.java
+++ b/backend/src/main/java/org/sejongisc/backend/admin/service/AdminUserService.java
@@ -113,8 +113,8 @@ public void updateUserRole(UUID userId, Role role) {
      * 특정 사용자를 선배(SENIOR) 등급으로 변경
      */
     @Transactional
-    public void promoteToSenior(UUID userId) {
-        userService.promoteToSenior(userId);
+    public void updateUserGrade(UUID userId, Grade grade) {
+        userService.updateUserGrade(userId, grade);
     }
 
     /**
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/controller/AttendanceRoundController.java b/backend/src/main/java/org/sejongisc/backend/attendance/controller/AttendanceRoundController.java
index 3ea0e321..6bd60eed 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/controller/AttendanceRoundController.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/controller/AttendanceRoundController.java
@@ -101,7 +101,7 @@ public ResponseEntity<AttendanceRoundResponse> createRound(
       - **필요**
       
       ## 권한
-      - **세션 MANAGER** 또는 **OWNER**
+      - **세션 OWNER**
       
       ## 경로 파라미터
       - **`roundId`**: 삭제할 라운드 ID (`UUID`)
@@ -137,7 +137,7 @@ public ResponseEntity<Void> deleteRound(
         ## 인증(JWT): **필요**
         
         ## 권한
-        - **세션 MEMBER**
+        - **세션 MEMBER/MANAGER/OWNER**
         
         ## 동작 설명
         - 특정 라운드 ID(`roundId`)를 통해 회차의 상세 정보 조회
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/controller/AttendanceSessionController.java b/backend/src/main/java/org/sejongisc/backend/attendance/controller/AttendanceSessionController.java
index 6504bfb5..b370e0f1 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/controller/AttendanceSessionController.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/controller/AttendanceSessionController.java
@@ -52,6 +52,9 @@ public class AttendanceSessionController {
           - **`description`**: 세션 상세 설명
           - **`allowedMinutes`**: 지각 처리 전 체크인 허용 시간 (분 단위)
           
+          ## 권한
+          - positionName: **회장, 부회장, 팀장**
+          
           ## 동작 설명
           - 새로운 출석 세션(Session) 엔티티 생성
           - 세션 상태(`SessionStatus`)는 기본적으로 **OPEN**으로 설정
@@ -157,6 +160,9 @@ public ResponseEntity<List<AttendanceSessionResponse>> getActiveSessions() {
       description = """
           ## 인증(JWT): **필요**
           
+          ## 권한
+          - **세션 OWNER**
+          
           ## 요청 파라미터 ( `AttendanceSessionRequest` )
           - **`title`**: 세션 제목
           - **`description`**: 세션 설명
@@ -189,7 +195,7 @@ public ResponseEntity<Void> updateSession(
       - **필요**
       
       ## 권한
-      - **세션 MANAGER** 또는 **OWNER**
+      - **세션 OWNER**
       
       ## 경로 파라미터
       - **`sessionId`**: 종료할 세션 ID (`UUID`)
@@ -223,7 +229,7 @@ public ResponseEntity<Void> closeSession(
       - **필요**
       
       ## 권한
-      - **세션 MANAGER** 또는 **OWNER**
+      - **세션 OWNER**
       
       ## 경로 파라미터
       - **`sessionId`**: 삭제할 세션 ID (`UUID`)
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/controller/SessionUserController.java b/backend/src/main/java/org/sejongisc/backend/attendance/controller/SessionUserController.java
index 7c1f6cd6..90b33d9e 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/controller/SessionUserController.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/controller/SessionUserController.java
@@ -155,7 +155,7 @@ public ResponseEntity<List<SessionUserResponse>> getSessionUsers(
           """
   )
   @PostMapping("/{sessionId}/users/add-all")
-  @PreAuthorize("hasRole('PRESIDENT')")
+  @PreAuthorize("hasAnyRole('PRESIDENT', 'SYSTEM_ADMIN')")
   public ResponseEntity<Void> addAllUsers(
       @PathVariable UUID sessionId,
       @AuthenticationPrincipal CustomUserDetails userDetails
@@ -164,4 +164,52 @@ public ResponseEntity<Void> addAllUsers(
     sessionUserService.addAllUsers(sessionId, adminUserId);
     return ResponseEntity.ok().build();
   }
+
+  /**
+   * 세션 관리자(MANAGER) 권한 부여
+   */
+  @Operation(
+      summary = "세션 관리자 추가",
+      description = """
+    ## 권한
+    - **세션 OWNER**
+    
+    ## 동작 설명
+    - 특정 사용자의 역할을 `MANAGER`로 격상시킵니다.
+    """)
+  @PostMapping("/{sessionId}/admins/{userId}")
+  public ResponseEntity<Void> addAdminToSession(
+      @PathVariable UUID sessionId,
+      @PathVariable UUID userId,
+      @AuthenticationPrincipal CustomUserDetails userDetails) {
+
+    UUID adminUserId = requireUserId(userDetails);
+    // 서비스단에서 세션 소유자(OWNER)인지 검증하는 로직이 포함되어야 함
+    sessionUserService.addAdmin(sessionId, userId, adminUserId);
+    return ResponseEntity.ok().build();
+  }
+
+  /**
+   * 세션 관리자(MANAGER) 권한 해제
+   */
+  @Operation(
+      summary = "세션 관리자 제거",
+      description = """
+    ## 권한
+    - **세션 OWNER**
+    
+    ## 동작 설명
+    - 특정 사용자의 역할을 `PARTICIPANT`로 강등시킵니다.
+    - `OWNER`는 강등될 수 없습니다.
+    """)
+  @DeleteMapping("/{sessionId}/admins/{userId}")
+  public ResponseEntity<Void> removeAdminFromSession(
+      @PathVariable UUID sessionId,
+      @PathVariable UUID userId,
+      @AuthenticationPrincipal CustomUserDetails userDetails) {
+
+    UUID adminUserId = requireUserId(userDetails);
+    sessionUserService.removeAdmin(sessionId, userId, adminUserId);
+    return ResponseEntity.noContent().build();
+  }
 }
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/repository/AttendanceRepository.java b/backend/src/main/java/org/sejongisc/backend/attendance/repository/AttendanceRepository.java
index 5c0ce450..5a281d8b 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/repository/AttendanceRepository.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/repository/AttendanceRepository.java
@@ -7,6 +7,7 @@
 import org.sejongisc.backend.attendance.entity.AttendanceRound;
 import org.sejongisc.backend.user.entity.User;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Modifying;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
@@ -33,4 +34,10 @@ void deleteAllByAttendanceRound_AttendanceSession_AttendanceSessionIdAndUser_Use
   Optional<Attendance> findByAttendanceRound_RoundIdAndUser(@Param("roundId") UUID roundId, @Param("user") User user);
 
   List<Attendance> findAllByAttendanceRound(AttendanceRound round);
+
+  @Modifying(clearAutomatically = true) // 벌크 연산 후 영속성 컨텍스트 동기화
+  @Query("DELETE FROM Attendance a " +
+      "WHERE a.attendanceRound IN " +
+      "(SELECT r FROM AttendanceRound r WHERE r.attendanceSession.attendanceSessionId = :sessionId)")
+  void deleteBySessionId(@Param("sessionId") UUID sessionId);
 }
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/repository/AttendanceRoundRepository.java b/backend/src/main/java/org/sejongisc/backend/attendance/repository/AttendanceRoundRepository.java
index 4ae9d0c7..242091d4 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/repository/AttendanceRoundRepository.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/repository/AttendanceRoundRepository.java
@@ -31,14 +31,14 @@ public interface AttendanceRoundRepository extends JpaRepository<AttendanceRound
 
     @Modifying(clearAutomatically = true, flushAutomatically = true)
     @Query("""
-    update AttendanceRound r
-    set r.roundStatus = 'CLOSED'
-    where r.roundStatus <> 'CLOSED'
-      and r.closeAt <= :now
-""")
+        update AttendanceRound r
+        set r.roundStatus = 'CLOSED'
+        where r.roundStatus <> 'CLOSED'
+          and r.closeAt <= :now
+    """)
     int closeDueRounds(LocalDateTime now);
 
-  List<AttendanceRound> findByRoundStatusAndCloseAtBefore(RoundStatus status, LocalDateTime dateTime);
+    List<AttendanceRound> findByRoundStatusAndCloseAtBefore(RoundStatus status, LocalDateTime dateTime);
 
     Optional<AttendanceRound> findByQrSecret(String qrCode);
     List<AttendanceRound> findByAttendanceSession_AttendanceSessionId(UUID sessionId);
@@ -89,4 +89,8 @@ List<AttendanceRound> findBySession_SessionIdAndRoundDateBefore(
     List<AttendanceRound> findBySession_SessionIdAndRoundDateAfterOrEqual(
             @Param("sessionId") UUID sessionId,
             @Param("date") LocalDate date);
+
+    @Modifying
+    @Query("DELETE FROM AttendanceRound a WHERE a.attendanceSession.attendanceSessionId = :sessionId")
+    void deleteBySessionId(@Param("sessionId") UUID sessionId);
 }
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/repository/SessionUserRepository.java b/backend/src/main/java/org/sejongisc/backend/attendance/repository/SessionUserRepository.java
index 2b3d511d..c3796fdc 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/repository/SessionUserRepository.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/repository/SessionUserRepository.java
@@ -25,7 +25,9 @@ public interface SessionUserRepository extends JpaRepository<SessionUser, UUID>
 
     List<SessionUser> findByAttendanceSession_AttendanceSessionId(UUID sessionId);
 
-
+    @Modifying
+    @Query("DELETE FROM SessionUser a WHERE a.attendanceSession.attendanceSessionId = :sessionId")
+    void deleteBySessionId(@Param("sessionId") UUID sessionId);
 
 
     /**
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceRoundService.java b/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceRoundService.java
index 27a53263..efa6352e 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceRoundService.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceRoundService.java
@@ -167,7 +167,7 @@ public void deleteRound(UUID roundId, UUID userId) {
         .orElseThrow(() -> new CustomException(ErrorCode.ROUND_NOT_FOUND));
 
     UUID sessionId = round.getAttendanceSession().getAttendanceSessionId();
-    authorizationService.ensureAdmin(sessionId, userId);
+    authorizationService.ensureOwner(sessionId, userId);
 
     attendanceRoundRepository.delete(round);
     log.info("라운드 삭제 완료 - roundId: {}", roundId);
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceService.java b/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceService.java
index 12e018c1..8272defd 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceService.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceService.java
@@ -113,6 +113,7 @@ public AttendanceResponse updateAttendanceStatusByRound(
       UUID targetUserId,
       AttendanceStatusUpdateRequest request
   ) {
+    // todo: activityLog 추가
     String status = (request.getStatus() == null) ? null : request.getStatus().toString();
     String reason = request.getReason();
 
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceSessionService.java b/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceSessionService.java
index 358cd5f4..45f5bfbe 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceSessionService.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/service/AttendanceSessionService.java
@@ -8,6 +8,8 @@
 import org.sejongisc.backend.attendance.entity.SessionRole;
 import org.sejongisc.backend.attendance.entity.SessionStatus;
 import org.sejongisc.backend.attendance.entity.SessionUser;
+import org.sejongisc.backend.attendance.repository.AttendanceRepository;
+import org.sejongisc.backend.attendance.repository.AttendanceRoundRepository;
 import org.sejongisc.backend.attendance.repository.AttendanceSessionRepository;
 import org.sejongisc.backend.attendance.repository.SessionUserRepository;
 import org.sejongisc.backend.common.exception.CustomException;
@@ -27,6 +29,8 @@
 @Slf4j
 public class AttendanceSessionService {
 
+  private final AttendanceRoundRepository attendanceRoundRepository;
+  private final AttendanceRepository attendanceRepository;
   private final AttendanceSessionRepository attendanceSessionRepository;
   private final UserRepository userRepository;
   private final SessionUserRepository sessionUserRepository;
@@ -37,7 +41,11 @@ public class AttendanceSessionService {
    */
   @Transactional
   public void createSession(UUID creatorId, AttendanceSessionRequest request) {
-
+    User creator = userRepository.findById(creatorId)
+        .orElseThrow(() -> new CustomException(ErrorCode.USER_NOT_FOUND));
+    if (!creator.isManagerPosition()) {
+      throw new CustomException(ErrorCode.NOT_MANAGER_POSITION);
+    }
     // 출석 세션 엔티티 생성
     AttendanceSession attendanceSession = AttendanceSession.builder()
         .title(request.title())
@@ -48,8 +56,6 @@ public void createSession(UUID creatorId, AttendanceSessionRequest request) {
 
     AttendanceSession saved = attendanceSessionRepository.save(attendanceSession);
 
-    User creator = userRepository.findById(creatorId)
-        .orElseThrow(() -> new CustomException(ErrorCode.USER_NOT_FOUND));
 
     // 세션 생성자를 OWNER로 세션 사용자에 추가
     SessionUser su = SessionUser.builder()
@@ -108,7 +114,7 @@ public List<AttendanceSessionResponse> getActiveSessions() {
    */
   public void updateSession(UUID sessionId, AttendanceSessionRequest request, UUID userId) {
     // 권한 확인
-    attendanceAuthorizationService.ensureAdmin(sessionId, userId);
+    attendanceAuthorizationService.ensureOwner(sessionId, userId);
 
     AttendanceSession session = attendanceSessionRepository.findById(sessionId)
         .orElseThrow(() -> new CustomException(ErrorCode.SESSION_NOT_FOUND));
@@ -128,11 +134,21 @@ public void updateSession(UUID sessionId, AttendanceSessionRequest request, UUID
    */
   public void deleteSession(UUID sessionId, UUID userId) {
     // 권한 확인
-    attendanceAuthorizationService.ensureAdmin(sessionId, userId);
+    attendanceAuthorizationService.ensureOwner(sessionId, userId);
 
     AttendanceSession session = attendanceSessionRepository.findById(sessionId)
         .orElseThrow(() -> new CustomException(ErrorCode.SESSION_NOT_FOUND));
 
+    // 최하위 자식인 Attendance(출석기록) 삭제
+    attendanceRepository.deleteBySessionId(sessionId);
+
+    // 중간 자식인 AttendanceRound(라운드) 삭제
+    attendanceRoundRepository.deleteBySessionId(sessionId);
+
+    // 참여자 명단(SessionUser) 삭제
+    sessionUserRepository.deleteBySessionId(sessionId);
+
+    // session 삭제
     attendanceSessionRepository.delete(session);
     log.info("출석 세션 삭제 완료: 세션ID={}", sessionId);
   }
@@ -141,7 +157,7 @@ public void deleteSession(UUID sessionId, UUID userId) {
    * 세션 수동 종료(해당 세션 관리자용) - 세션 상태를 CLOSED로 변경 - 체크인 비활성화
    */
   public void closeSession(UUID sessionId, UUID userId) {
-    attendanceAuthorizationService.ensureAdmin(sessionId, userId);
+    attendanceAuthorizationService.ensureOwner(sessionId, userId);
 
     AttendanceSession session = attendanceSessionRepository.findById(sessionId)
         .orElseThrow(() -> new CustomException(ErrorCode.SESSION_NOT_FOUND));
diff --git a/backend/src/main/java/org/sejongisc/backend/attendance/service/SessionUserService.java b/backend/src/main/java/org/sejongisc/backend/attendance/service/SessionUserService.java
index ee87b4e8..ba250492 100644
--- a/backend/src/main/java/org/sejongisc/backend/attendance/service/SessionUserService.java
+++ b/backend/src/main/java/org/sejongisc/backend/attendance/service/SessionUserService.java
@@ -35,7 +35,7 @@ public class SessionUserService {
 
   public void addAllUsers(UUID sessionId, UUID userId) {
     // 권한 확인
-    authorizationService.ensureAdmin(sessionId, userId);
+    authorizationService.ensureOwner(sessionId, userId);
     log.info("세션에 모든 사용자 추가 시작: 세션ID={}", sessionId);
 
     AttendanceSession session = attendanceSessionRepository.findById(sessionId)
@@ -99,7 +99,7 @@ public SessionUserResponse addUserToSession(UUID sessionId, UUID targetUserId, U
   public void removeUserFromSession(UUID sessionId, UUID targetUserId, UUID actorUserId) {
     authorizationService.ensureOwner(sessionId, actorUserId);
 
-    AttendanceSession session = attendanceSessionRepository.findById(sessionId)
+    attendanceSessionRepository.findById(sessionId)
         .orElseThrow(() -> new CustomException(ErrorCode.SESSION_NOT_FOUND));
 
     // SessionUser 삭제
@@ -124,11 +124,6 @@ public List<SessionUserResponse> getSessionUsers(UUID sessionId, UUID viewerUser
     return users.stream().map(SessionUserResponse::from).toList();
   }
 
-  @Transactional(readOnly = true)
-  public boolean isUserInSession(UUID sessionId, UUID userId) {
-    return sessionUserRepository.existsByAttendanceSession_AttendanceSessionIdAndUser_UserId(sessionId, userId);
-  }
-
   private void createAbsentForPastRounds(UUID sessionId, User user) {
     List<AttendanceRound> pastRounds = attendanceRoundRepository
         .findByAttendanceSession_AttendanceSessionIdAndRoundDateBefore(sessionId, LocalDate.now());
@@ -150,47 +145,13 @@ private void createAbsentForPastRounds(UUID sessionId, User user) {
     }
   }
 
-  /**
-   * 세션 가입
-   */
-  @Transactional
-  public void joinSession(UUID sessionId, UUID userId) {
-    // 이미 가입했는지 체크
-    boolean exists = sessionUserRepository.existsByAttendanceSession_AttendanceSessionIdAndUser_UserId(sessionId,
-        userId);
-    if (exists) {
-      throw new CustomException(ErrorCode.ALREADY_JOINED);
-    }
-
-    AttendanceSession session = attendanceSessionRepository.findById(sessionId)
-        .orElseThrow(() -> new CustomException(ErrorCode.SESSION_NOT_FOUND));
-    User user = userRepository.findById(userId)
-        .orElseThrow(() -> new CustomException(ErrorCode.USER_NOT_FOUND));
-
-    sessionUserRepository.save(SessionUser.builder()
-        .attendanceSession(session)
-        .user(user)
-        .sessionRole(SessionRole.PARTICIPANT)
-        .build());
-  }
-
-  /**
-   * 세션 탈퇴
-   */
-  @Transactional
-  public void leaveSession(UUID sessionId, UUID userId) {
-    SessionUser su = sessionUserRepository
-        .findByAttendanceSession_AttendanceSessionIdAndUser_UserId(sessionId, userId)
-        .orElseThrow(() -> new CustomException(ErrorCode.NOT_SESSION_MEMBER));
-
-    sessionUserRepository.delete(su);
-  }
 
   /**
    * 세션 관리자 추가/제거
    */
   @Transactional
-  public void addAdmin(UUID sessionId, UUID targetUserId) {
+  public void addAdmin(UUID sessionId, UUID targetUserId, UUID actorUserId) {
+    authorizationService.ensureOwner(sessionId, actorUserId);
     SessionUser su = sessionUserRepository
         .findByAttendanceSession_AttendanceSessionIdAndUser_UserId(sessionId, targetUserId)
         .orElseThrow(() -> new CustomException(ErrorCode.TARGET_NOT_SESSION_MEMBER));
@@ -198,7 +159,8 @@ public void addAdmin(UUID sessionId, UUID targetUserId) {
   }
 
   @Transactional
-  public void removeAdmin(UUID sessionId, UUID targetUserId) {
+  public void removeAdmin(UUID sessionId, UUID targetUserId, UUID actorUserId) {
+    authorizationService.ensureOwner(sessionId, actorUserId);
     SessionUser su = sessionUserRepository
         .findByAttendanceSession_AttendanceSessionIdAndUser_UserId(sessionId, targetUserId)
         .orElseThrow(() -> new CustomException(ErrorCode.TARGET_NOT_SESSION_MEMBER));
diff --git a/backend/src/main/java/org/sejongisc/backend/common/exception/ErrorCode.java b/backend/src/main/java/org/sejongisc/backend/common/exception/ErrorCode.java
index 31ede69a..5219ac70 100644
--- a/backend/src/main/java/org/sejongisc/backend/common/exception/ErrorCode.java
+++ b/backend/src/main/java/org/sejongisc/backend/common/exception/ErrorCode.java
@@ -89,30 +89,45 @@ public enum ErrorCode {
   // USER
 
   USER_NOT_FOUND(HttpStatus.NOT_FOUND, "유저를 찾을 수 없습니다."),
+
   DUPLICATE_EMAIL(HttpStatus.CONFLICT, "이미 가입된 이메일입니다."),
+
   DUPLICATE_PHONE(HttpStatus.CONFLICT, "이미 사용 중인 전화번호입니다."),
+
   DUPLICATE_USER(HttpStatus.CONFLICT, "이미 가입된 사용자입니다."),
+
   INVALID_INPUT(HttpStatus.BAD_REQUEST, "입력값이 올바르지 않습니다."),
+
   USER_WITHDRAWN(HttpStatus.FORBIDDEN, "탈퇴한 회원은 로그인할 수 없습니다."),
+
   NEED_PENDING_APPROVAL(HttpStatus.FORBIDDEN, "가입 승인 대기 중입니다. 관리자의 확인 후 이용 가능합니다"),
 
+  NOT_MANAGER_POSITION(HttpStatus.FORBIDDEN, "관리자 포지션만 가능한 기능입니다. (팀장, 부회장, 회장)"),
+
   // EXCEL
 
   INVALID_FILE_FORMAT(HttpStatus.BAD_REQUEST, "지원하지 않는 파일 형식입니다. .xlsx 파일을 업로드해주세요."),
-  INVALID_EXCEL_STRUCTURE(HttpStatus.UNPROCESSABLE_ENTITY, "엑셀 양식이 일치하지 않습니다. 필수 컬럼을 확인해주세요."),
-  EMPTY_FILE(HttpStatus.BAD_REQUEST, "업로드된 파일이 비어있습니다."),
 
+  INVALID_EXCEL_STRUCTURE(HttpStatus.UNPROCESSABLE_ENTITY, "엑셀 양식이 일치하지 않습니다. 필수 컬럼을 확인해주세요."),
 
+  EMPTY_FILE(HttpStatus.BAD_REQUEST, "업로드된 파일이 비어있습니다."),
 
   // BETTING
 
   STOCK_NOT_FOUND(HttpStatus.NOT_FOUND, "주식 종목이 존재하지 않습니다."),
+
   BET_ROUND_NOT_FOUND(HttpStatus.NOT_FOUND, "존재하지 않는 라운드입니다."),
+
   BET_DUPLICATE(HttpStatus.CONFLICT, "이미 이 라운드에 베팅했습니다."),
+
   BET_ROUND_CLOSED(HttpStatus.CONFLICT, "베팅 가능 시간이 아닙니다."),
+
   BET_NOT_FOUND(HttpStatus.NOT_FOUND, "해당 베팅을 찾을 수 없습니다."),
+
   BET_POINT_TOO_LOW(HttpStatus.CONFLICT, "베팅 포인트는 10 이상이어야 합니다."),
+
   BET_ROUND_NOT_CLOSED(HttpStatus.CONFLICT, "닫히지 않은 배팅입니다."),
+
   BET_ALREADY_PROCESSED(HttpStatus.CONFLICT, "이미 취소되었거나 처리된 베팅입니다."),
 
   // BOARD
diff --git a/backend/src/main/java/org/sejongisc/backend/user/controller/UserController.java b/backend/src/main/java/org/sejongisc/backend/user/controller/UserController.java
index ca50e006..f6ab1ed0 100644
--- a/backend/src/main/java/org/sejongisc/backend/user/controller/UserController.java
+++ b/backend/src/main/java/org/sejongisc/backend/user/controller/UserController.java
@@ -15,7 +15,8 @@
 import org.sejongisc.backend.common.auth.service.RefreshTokenService;
 import org.sejongisc.backend.user.dto.*;
 import org.sejongisc.backend.user.service.UserService;
-import org.springframework.data.domain.Slice;
+import org.springframework.data.domain.*;
+import org.springframework.data.web.PageableDefault;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -58,15 +59,19 @@ public ResponseEntity<Void> updateUser(@RequestBody @Valid UserUpdateRequest req
     return ResponseEntity.ok().build();
   }
 
-  @Operation(summary = "내 출석 로그 조회")
+  @Operation(summary = "내 출석 로그 조회", description = "?page=0&size=20 방식으로 페이지네이션 조회 (최신순)")
   @GetMapping("/logs/attendance")
-  public ResponseEntity<List<ActivityLog>> getAttendanceLogs(@AuthenticationPrincipal CustomUserDetails customUserDetails) {
-    return ResponseEntity.ok(userService.getAttendanceActivityLog(customUserDetails.getUserId()));
+  public ResponseEntity<Page<ActivityLog>> getAttendanceLogs(
+      @AuthenticationPrincipal CustomUserDetails customUserDetails,
+      @PageableDefault(size = 20, sort = "createdAt", direction = Sort.Direction.DESC) Pageable pageable) {
+    return ResponseEntity.ok(userService.getAttendanceActivityLog(customUserDetails.getUserId(), pageable));
   }
 
-  @Operation(summary = "내 활동 로그 조회")
+  @Operation(summary = "내 활동 로그 조회", description = "?page=0&size=20 방식으로 페이지네이션 조회 (최신순)")
   @GetMapping("/logs/board")
-  public ResponseEntity<List<ActivityLog>> getBoardLogs(@AuthenticationPrincipal CustomUserDetails customUserDetails) {
-    return ResponseEntity.ok(userService.getBoardActivityLog(customUserDetails.getUserId()));
+  public ResponseEntity<Page<ActivityLog>> getBoardLogs(
+      @AuthenticationPrincipal CustomUserDetails customUserDetails,
+      @PageableDefault(size = 20, sort = "createdAt", direction = Sort.Direction.DESC) Pageable pageable) {
+    return ResponseEntity.ok(userService.getBoardActivityLog(customUserDetails.getUserId(), pageable));
   }
 }
diff --git a/backend/src/main/java/org/sejongisc/backend/user/entity/Grade.java b/backend/src/main/java/org/sejongisc/backend/user/entity/Grade.java
index d405b49b..e33ceb6c 100644
--- a/backend/src/main/java/org/sejongisc/backend/user/entity/Grade.java
+++ b/backend/src/main/java/org/sejongisc/backend/user/entity/Grade.java
@@ -4,14 +4,15 @@ public enum Grade {
   NEW_MEMBER, // 신입부원
   ASSOCIATE_MEMBER, // 준회원
   REGULAR_MEMBER, // 정회원
-  SENIOR; // 선배/OB
+  //SENIOR        // 선배/OB는 정회원으로 대체
+  ;
 
   public static Grade fromString(String gradeStr) {
     if (gradeStr == null) return NEW_MEMBER;
 
     if (gradeStr.contains("정회원")) return REGULAR_MEMBER;
     if (gradeStr.contains("준회원")) return ASSOCIATE_MEMBER;
-    if (gradeStr.contains("선배") || gradeStr.contains("OB")) return SENIOR;
+    //if (gradeStr.contains("선배") || gradeStr.contains("OB")) return SENIOR;
 
     return NEW_MEMBER;
   }
diff --git a/backend/src/main/java/org/sejongisc/backend/user/entity/User.java b/backend/src/main/java/org/sejongisc/backend/user/entity/User.java
index ff1ba46d..b045d173 100644
--- a/backend/src/main/java/org/sejongisc/backend/user/entity/User.java
+++ b/backend/src/main/java/org/sejongisc/backend/user/entity/User.java
@@ -68,7 +68,7 @@ public class User extends BasePostgresEntity{
     @Enumerated(EnumType.STRING)        // 새 장부 업로드 시: 기존에 ACTIVE한 모든 인원을 INACTIVE로 일괄 업데이트
     @Column(nullable = false)           // 새 엑셀에 있는 studentId을 대조하여, 명단에 있는 사람만 다시 ACTIVE로 바꾸고
     @Builder.Default                    // generation(기수)과 positionName(직위)을 최신화
-    private UserStatus status = UserStatus.ACTIVE; // 활동 상태 (ACTIVE, INACTIVE, GRADUATED, OUT 등)
+    private UserStatus status = UserStatus.ACTIVE; // 활동 상태 (ACTIVE, INACTIVE, OUT 등)
 
     @Column(columnDefinition = "integer default 0",nullable = false)
     private Integer point;
@@ -85,11 +85,12 @@ public class User extends BasePostgresEntity{
 
     // 권한 확인용 편의 메서드
     public boolean isManagerPosition() {
-        if (this.positionName == null) return false;
+        if (this.role == Role.TEAM_MEMBER || this.role == Role.PENDING_MEMBER ) return false;
         // 직위에 '팀장', '대표', '부대표' 등의 키워드가 있으면 운영진 권한 부여 후보
-        return this.positionName.contains("팀장") ||
-            this.positionName.contains("대표") ||
-            this.positionName.contains("회장");
+        return this.role == Role.SYSTEM_ADMIN ||
+            this.role == Role.PRESIDENT ||
+            this.role == Role.VICE_PRESIDENT ||
+            this.role == Role.TEAM_LEADER;
     }
 
     // 기본값 지정
diff --git a/backend/src/main/java/org/sejongisc/backend/user/entity/UserStatus.java b/backend/src/main/java/org/sejongisc/backend/user/entity/UserStatus.java
index 4882ea16..28790628 100644
--- a/backend/src/main/java/org/sejongisc/backend/user/entity/UserStatus.java
+++ b/backend/src/main/java/org/sejongisc/backend/user/entity/UserStatus.java
@@ -9,7 +9,7 @@
 public enum UserStatus {
   ACTIVE("활동 중"),
   INACTIVE("활동 중지"),
-  GRADUATED("졸업생"),
+  //GRADUATED("졸업생"),
   OUT("탈퇴");
 
   private final String description; // 한글 명칭
diff --git a/backend/src/main/java/org/sejongisc/backend/user/service/UserService.java b/backend/src/main/java/org/sejongisc/backend/user/service/UserService.java
index f583d33b..7d408716 100644
--- a/backend/src/main/java/org/sejongisc/backend/user/service/UserService.java
+++ b/backend/src/main/java/org/sejongisc/backend/user/service/UserService.java
@@ -15,6 +15,8 @@
 import org.sejongisc.backend.user.entity.UserStatus;
 import org.sejongisc.backend.user.repository.UserRepository;
 import org.sejongisc.backend.user.util.PasswordPolicyValidator;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.Pageable;
 import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -61,15 +63,17 @@ public void updateUser(UUID userId, UserUpdateRequest request) {
     }
 
     @Transactional(readOnly = true)
-    public List<ActivityLog> getAttendanceActivityLog(UUID userId) {
-        return activityLogRepository.findByUserIdAndActivityTypesOrderByCreatedAtDesc(userId,
-                List.of(ActivityType.ATTENDANCE));
+    public Page<ActivityLog> getAttendanceActivityLog(UUID userId, Pageable pageable) {
+        return activityLogRepository.findByUserIdAndActivityTypeIn(userId,
+            List.of(ActivityType.ATTENDANCE),
+            pageable);
     }
 
     @Transactional(readOnly = true)
-    public List<ActivityLog> getBoardActivityLog(UUID userId) {
-        return activityLogRepository.findByUserIdAndActivityTypesOrderByCreatedAtDesc(userId,
-                List.of(ActivityType.BOARD_LIKE, ActivityType.BOARD_POST, ActivityType.BOARD_COMMENT));
+    public Page<ActivityLog> getBoardActivityLog(UUID userId, Pageable pageable) {
+        return activityLogRepository.findByUserIdAndActivityTypeIn(userId,
+            List.of(ActivityType.BOARD_LIKE, ActivityType.BOARD_POST, ActivityType.BOARD_COMMENT),
+            pageable);
     }
 
     @Transactional
@@ -98,13 +102,9 @@ public void updateUserRole(UUID userId, Role role) {
     }
 
     @Transactional
-    public void promoteToSenior(UUID userId) {
+    public void updateUserGrade(UUID userId, Grade grade) {
         User user = findUser(userId);
-
-        // grade 및 status 변경
-        user.setGrade(Grade.SENIOR);
-        user.setStatus(UserStatus.GRADUATED);
-
+        user.setGrade(grade);
         log.info("선배 등급 전환 완료: userId={}, 학번={}", userId, user.getStudentId());
     }