diff --git a/src/main/java/edu/handong/csee/histudy/controller/form/ReportForm.java b/src/main/java/edu/handong/csee/histudy/controller/form/ReportForm.java
index 1d939be..42df88e 100644
--- a/src/main/java/edu/handong/csee/histudy/controller/form/ReportForm.java
+++ b/src/main/java/edu/handong/csee/histudy/controller/form/ReportForm.java
@@ -1,6 +1,9 @@
 package edu.handong.csee.histudy.controller.form;
 
-import edu.handong.csee.histudy.domain.*;
+import edu.handong.csee.histudy.domain.GroupCourse;
+import edu.handong.csee.histudy.domain.GroupReport;
+import edu.handong.csee.histudy.domain.StudyGroup;
+import edu.handong.csee.histudy.domain.User;
 import io.swagger.v3.oas.annotations.media.Schema;
 import lombok.*;
 
@@ -23,10 +26,10 @@ public class ReportForm {
     private Long totalMinutes;
 
     /**
-     * Contains student ID
+     * Contains student ID(PK)
      */
-    @Schema(description = "Participant SIDs of the report", type = "array", example = "[\"20200001\", \"20200002\"]")
-    private List<String> participants = new ArrayList<>();
+    @Schema(description = "Participant ID(PK) of the report", type = "array", example = "[1, 2]")
+    private List<Long> participants = new ArrayList<>();
 
     /**
      * Contains image URL
diff --git a/src/main/java/edu/handong/csee/histudy/service/ReportService.java b/src/main/java/edu/handong/csee/histudy/service/ReportService.java
index 5119a27..5aa5c47 100644
--- a/src/main/java/edu/handong/csee/histudy/service/ReportService.java
+++ b/src/main/java/edu/handong/csee/histudy/service/ReportService.java
@@ -31,7 +31,7 @@ public ReportDto.ReportInfo createReport(ReportForm form, String email) {
 
         List<User> participants = form.getParticipants()
                 .stream()
-                .map(userRepository::findUserBySid)
+                .map(userRepository::findById)
                 .filter(Optional::isPresent)
                 .map(Optional::get)
                 .toList();
@@ -75,7 +75,7 @@ public List<ReportDto.ReportInfo> getAllReports() {
     public boolean updateReport(Long reportId, ReportForm form) {
         List<User> participants = form.getParticipants()
                 .stream()
-                .map(userRepository::findUserBySid)
+                .map(userRepository::findById)
                 .filter(Optional::isPresent)
                 .map(Optional::get)
                 .toList();
diff --git a/src/test/java/edu/handong/csee/histudy/group/ReportGroupCourseServiceTest.java b/src/test/java/edu/handong/csee/histudy/group/ReportGroupCourseServiceTest.java
index 2c3f7c1..4839276 100644
--- a/src/test/java/edu/handong/csee/histudy/group/ReportGroupCourseServiceTest.java
+++ b/src/test/java/edu/handong/csee/histudy/group/ReportGroupCourseServiceTest.java
@@ -173,7 +173,7 @@ public void teamReportViewTest() {
                 .title("title")
                 .content("content")
                 .totalMinutes(60L)
-                .participants(List.of("22000328"))
+                .participants(List.of(savedB.getId()))
                 .courses(List.of(1L, 2L, 3L))
                 .build();
         reportService.createReport(form, "a@b.com");
diff --git a/src/test/java/edu/handong/csee/histudy/report/ReportCourseReportServiceTestGroup.java b/src/test/java/edu/handong/csee/histudy/report/ReportCourseReportServiceTestGroup.java
index cc48db4..1c7c83d 100644
--- a/src/test/java/edu/handong/csee/histudy/report/ReportCourseReportServiceTestGroup.java
+++ b/src/test/java/edu/handong/csee/histudy/report/ReportCourseReportServiceTestGroup.java
@@ -84,7 +84,7 @@ public void reportServiceTest() {
                 .title("title")
                 .content("content")
                 .totalMinutes(60L)
-                .participants(List.of("22000328"))
+                .participants(List.of(userA.getId()))
                 .courses(List.of(course.getId(), courseB.getId(), courseC.getId()))
                 .build();
 
@@ -119,19 +119,20 @@ public void reportDetailTest() {
                 .semester(1)
                 .build();
         courseRepository.save(courseC);
-        ReportForm form = ReportForm.builder()
-                .title("title")
-                .content("content")
-                .totalMinutes(60L)
-                .participants(List.of("22000328"))
-                .courses(List.of(1L, 2L, 3L))
-                .build();
         User user = User.builder()
                 .sid("22000328")
                 .email("a@a.com")
                 .role(Role.USER)
                 .build();
         User saved = userRepository.save(user);
+        ReportForm form = ReportForm.builder()
+                .title("title")
+                .content("content")
+                .totalMinutes(60L)
+                .participants(List.of(saved.getId()))
+                .courses(List.of(1L, 2L, 3L))
+                .build();
+
         saved.selectCourse(List.of(course, courseB, courseC));
         StudyGroup studyGroup = studyGroupRepository.save(new StudyGroup(1, List.of(saved)));
 
diff --git a/src/test/java/edu/handong/csee/histudy/user/UserServiceTests.java b/src/test/java/edu/handong/csee/histudy/user/UserServiceTests.java
index 01d0dd2..ee8e313 100644
--- a/src/test/java/edu/handong/csee/histudy/user/UserServiceTests.java
+++ b/src/test/java/edu/handong/csee/histudy/user/UserServiceTests.java
@@ -126,7 +126,7 @@ public void userListTest() {
                 .title("title")
                 .content("content")
                 .totalMinutes(60L)
-                .participants(List.of("22000329"))
+                .participants(List.of(savedA.getId()))
                 .courses(List.of(1L, 2L, 3L))
                 .build();
         ReportDto.ReportInfo report = reportService.createReport(form, "a@a.com");
diff --git a/src/test/java/edu/handong/csee/integration/ReportTests.java b/src/test/java/edu/handong/csee/integration/ReportTests.java
index 693efeb..d31b15d 100644
--- a/src/test/java/edu/handong/csee/integration/ReportTests.java
+++ b/src/test/java/edu/handong/csee/integration/ReportTests.java
@@ -69,7 +69,7 @@ void ReportTests_18(@Value("${custom.jwt.example.admin}") String adminToken) thr
                 .title("title")
                 .content("content")
                 .totalMinutes(10L)
-                .participants(List.of(writer.getSid()))
+                .participants(List.of(writer.getId()))
                 .courses(List.of())
                 .build();