diff --git a/src/main/java/com/gdschongik/gdsc/domain/study/application/StudentStudyService.java b/src/main/java/com/gdschongik/gdsc/domain/study/application/StudentStudyService.java
index 1daeb72b0..0bc4af0c7 100644
--- a/src/main/java/com/gdschongik/gdsc/domain/study/application/StudentStudyService.java
+++ b/src/main/java/com/gdschongik/gdsc/domain/study/application/StudentStudyService.java
@@ -90,11 +90,14 @@ public void attend(Long studyDetailId, StudyAttendCreateRequest request) {
                 .orElseThrow(() -> new CustomException(STUDY_DETAIL_NOT_FOUND));
         final Member currentMember = memberUtil.getCurrentMember();
         final Study study = studyDetail.getStudy();
+        final boolean isAlreadyAttended =
+                attendanceRepository.existsByStudentIdAndStudyDetailId(currentMember.getId(), studyDetailId);
         final StudyHistory studyHistory = studyHistoryRepository
                 .findByStudentAndStudy(currentMember, study)
                 .orElseThrow(() -> new CustomException(STUDY_HISTORY_NOT_FOUND));
 
-        attendanceValidator.validateAttendance(studyDetail, request.attendanceNumber(), LocalDate.now());
+        attendanceValidator.validateAttendance(
+                studyDetail, request.attendanceNumber(), LocalDate.now(), isAlreadyAttended);
 
         Attendance attendance = Attendance.create(currentMember, studyDetail);
         attendanceRepository.save(attendance);
diff --git a/src/main/java/com/gdschongik/gdsc/domain/study/dao/AttendanceRepository.java b/src/main/java/com/gdschongik/gdsc/domain/study/dao/AttendanceRepository.java
index 4c8d83d20..d259ab9cd 100644
--- a/src/main/java/com/gdschongik/gdsc/domain/study/dao/AttendanceRepository.java
+++ b/src/main/java/com/gdschongik/gdsc/domain/study/dao/AttendanceRepository.java
@@ -3,4 +3,6 @@
 import com.gdschongik.gdsc.domain.study.domain.Attendance;
 import org.springframework.data.jpa.repository.JpaRepository;
 
-public interface AttendanceRepository extends JpaRepository<Attendance, Long>, AttendanceCustomRepository {}
+public interface AttendanceRepository extends JpaRepository<Attendance, Long>, AttendanceCustomRepository {
+    boolean existsByStudentIdAndStudyDetailId(Long studentId, Long studyDetailId);
+}
diff --git a/src/main/java/com/gdschongik/gdsc/domain/study/domain/AttendanceValidator.java b/src/main/java/com/gdschongik/gdsc/domain/study/domain/AttendanceValidator.java
index 2637fd41a..59532818c 100644
--- a/src/main/java/com/gdschongik/gdsc/domain/study/domain/AttendanceValidator.java
+++ b/src/main/java/com/gdschongik/gdsc/domain/study/domain/AttendanceValidator.java
@@ -8,7 +8,8 @@
 
 @DomainService
 public class AttendanceValidator {
-    public void validateAttendance(StudyDetail studyDetail, String attendanceNumber, LocalDate date) {
+    public void validateAttendance(
+            StudyDetail studyDetail, String attendanceNumber, LocalDate date, boolean isAlreadyAttended) {
         // 출석체크 날짜 검증
         LocalDate attendanceDay = studyDetail.getAttendanceDay();
         if (!attendanceDay.equals(date)) {
@@ -19,5 +20,10 @@ public void validateAttendance(StudyDetail studyDetail, String attendanceNumber,
         if (!studyDetail.getAttendanceNumber().equals(attendanceNumber)) {
             throw new CustomException(ATTENDANCE_NUMBER_MISMATCH);
         }
+
+        // 출석체크 번호 검증
+        if (isAlreadyAttended) {
+            throw new CustomException(STUDY_DETAIL_ALREADY_ATTENDED);
+        }
     }
 }
diff --git a/src/main/java/com/gdschongik/gdsc/global/exception/ErrorCode.java b/src/main/java/com/gdschongik/gdsc/global/exception/ErrorCode.java
index bec818fe9..069a55f0c 100644
--- a/src/main/java/com/gdschongik/gdsc/global/exception/ErrorCode.java
+++ b/src/main/java/com/gdschongik/gdsc/global/exception/ErrorCode.java
@@ -130,6 +130,7 @@ public enum ErrorCode {
     // Attendance
     ATTENDANCE_DATE_INVALID(HttpStatus.CONFLICT, "강의일이 아니면 출석체크할 수 없습니다."),
     ATTENDANCE_NUMBER_MISMATCH(HttpStatus.CONFLICT, "출석번호가 일치하지 않습니다."),
+    STUDY_DETAIL_ALREADY_ATTENDED(HttpStatus.CONFLICT, "이미 출석 처리된 스터디입니다."),
 
     // Order
     ORDER_NOT_FOUND(HttpStatus.NOT_FOUND, "주문이 존재하지 않습니다."),
diff --git a/src/test/java/com/gdschongik/gdsc/domain/study/domain/AttendanceValidatorTest.java b/src/test/java/com/gdschongik/gdsc/domain/study/domain/AttendanceValidatorTest.java
index b39091045..a394dff05 100644
--- a/src/test/java/com/gdschongik/gdsc/domain/study/domain/AttendanceValidatorTest.java
+++ b/src/test/java/com/gdschongik/gdsc/domain/study/domain/AttendanceValidatorTest.java
@@ -3,6 +3,7 @@
 import static com.gdschongik.gdsc.global.common.constant.StudyConstant.ATTENDANCE_NUMBER;
 import static com.gdschongik.gdsc.global.exception.ErrorCode.ATTENDANCE_DATE_INVALID;
 import static com.gdschongik.gdsc.global.exception.ErrorCode.ATTENDANCE_NUMBER_MISMATCH;
+import static com.gdschongik.gdsc.global.exception.ErrorCode.STUDY_DETAIL_ALREADY_ATTENDED;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import com.gdschongik.gdsc.domain.member.domain.Member;
@@ -36,7 +37,7 @@ class 스터디_출석체크시 {
 
             // when & then
             assertThatThrownBy(() -> attendanceValidator.validateAttendance(
-                            studyDetail, ATTENDANCE_NUMBER, attendanceDay.plusDays(1)))
+                            studyDetail, ATTENDANCE_NUMBER, attendanceDay.plusDays(1), false))
                     .isInstanceOf(CustomException.class)
                     .hasMessage(ATTENDANCE_DATE_INVALID.getMessage());
         }
@@ -55,10 +56,30 @@ class 스터디_출석체크시 {
             LocalDate attendanceDay = studyDetail.getAttendanceDay();
 
             // when & then
-            assertThatThrownBy(() ->
-                            attendanceValidator.validateAttendance(studyDetail, ATTENDANCE_NUMBER + 1, attendanceDay))
+            assertThatThrownBy(() -> attendanceValidator.validateAttendance(
+                            studyDetail, ATTENDANCE_NUMBER + 1, attendanceDay, false))
                     .isInstanceOf(CustomException.class)
                     .hasMessage(ATTENDANCE_NUMBER_MISMATCH.getMessage());
         }
+
+        @Test
+        void 이미_출석했다면_실패한다() {
+            // given
+            Member mentor = fixtureHelper.createAssociateMember(1L);
+
+            LocalDateTime now = LocalDateTime.now();
+            Period period = Period.createPeriod(now.plusDays(10), now.plusDays(65));
+            Period applicationPeriod = Period.createPeriod(now.minusDays(10), now.plusDays(5));
+            Study study = fixtureHelper.createStudy(mentor, period, applicationPeriod);
+            StudyDetail studyDetail = fixtureHelper.createStudyDetail(study, now, now.plusDays(7));
+
+            LocalDate attendanceDay = studyDetail.getAttendanceDay();
+
+            // when & then
+            assertThatThrownBy(() ->
+                            attendanceValidator.validateAttendance(studyDetail, ATTENDANCE_NUMBER, attendanceDay, true))
+                    .isInstanceOf(CustomException.class)
+                    .hasMessage(STUDY_DETAIL_ALREADY_ATTENDED.getMessage());
+        }
     }
 }