diff --git a/src/test/java/org/runnect/server/user/service/UserStampServiceTest.java b/src/test/java/org/runnect/server/user/service/UserStampServiceTest.java
new file mode 100644
index 0000000..eccac1e
--- /dev/null
+++ b/src/test/java/org/runnect/server/user/service/UserStampServiceTest.java
@@ -0,0 +1,253 @@
+package org.runnect.server.user.service;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.Optional;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.runnect.server.user.dto.response.GetUserStampsResponseDto;
+import org.runnect.server.user.entity.RunnectUser;
+import org.runnect.server.user.entity.SocialType;
+import org.runnect.server.user.entity.StampType;
+import org.runnect.server.user.entity.UserStamp;
+import org.runnect.server.user.exception.userException.NotFoundUserException;
+import org.runnect.server.user.repository.UserRepository;
+import org.runnect.server.user.repository.UserStampRepository;
+import org.springframework.test.util.ReflectionTestUtils;
+
+@ExtendWith(MockitoExtension.class)
+class UserStampServiceTest {
+
+    @Mock
+    private UserStampRepository userStampRepository;
+    @Mock
+    private UserRepository userRepository;
+
+    private UserStampService userStampService;
+
+    @BeforeEach
+    void setUp() {
+        userStampService = new UserStampService(userStampRepository, userRepository);
+    }
+
+    private RunnectUser buildUser(Long id) {
+        RunnectUser user = RunnectUser.builder()
+            .nickname("러너" + id)
+            .socialId("social-" + id)
+            .email("user" + id + "@runnect.io")
+            .provider(SocialType.KAKAO)
+            .build();
+        ReflectionTestUtils.setField(user, "id", id);
+        return user;
+    }
+
+    @Nested
+    @DisplayName("createStampByUser")
+    class CreateStampByUser {
+
+        @Test
+        @DisplayName("활동 카운트가 0이면 아무 것도 하지 않는다")
+        void 활동카운트_0() {
+            RunnectUser user = buildUser(1L);
+
+            userStampService.createStampByUser(user, StampType.c);
+
+            verify(userStampRepository, never()).save(any());
+        }
+
+        @Test
+        @DisplayName("코스 1개째면 c1 스탬프가 생성된다")
+        void 코스_1개_c1() {
+            RunnectUser user = buildUser(1L);
+            user.updateCreatedCourse();
+
+            userStampService.createStampByUser(user, StampType.c);
+
+            org.mockito.ArgumentCaptor<UserStamp> captor = org.mockito.ArgumentCaptor.forClass(UserStamp.class);
+            verify(userStampRepository).save(captor.capture());
+            assertThat(captor.getValue().getStampId()).isEqualTo(StampType.c1);
+        }
+
+        @Test
+        @DisplayName("코스 10개째면 c2 스탬프가 생성된다")
+        void 코스_10개_c2() {
+            RunnectUser user = buildUser(1L);
+            for (int i = 0; i < 10; i++) {
+                user.updateCreatedCourse();
+            }
+
+            userStampService.createStampByUser(user, StampType.c);
+
+            org.mockito.ArgumentCaptor<UserStamp> captor = org.mockito.ArgumentCaptor.forClass(UserStamp.class);
+            verify(userStampRepository).save(captor.capture());
+            assertThat(captor.getValue().getStampId()).isEqualTo(StampType.c2);
+        }
+
+        @Test
+        @DisplayName("코스 30개째면 c3 스탬프가 생성된다")
+        void 코스_30개_c3() {
+            RunnectUser user = buildUser(1L);
+            for (int i = 0; i < 30; i++) {
+                user.updateCreatedCourse();
+            }
+
+            userStampService.createStampByUser(user, StampType.c);
+
+            org.mockito.ArgumentCaptor<UserStamp> captor = org.mockito.ArgumentCaptor.forClass(UserStamp.class);
+            verify(userStampRepository).save(captor.capture());
+            assertThat(captor.getValue().getStampId()).isEqualTo(StampType.c3);
+        }
+
+        @Test
+        @DisplayName("기준 개수(1/10/30)가 아니면 스탬프를 생성하지 않는다")
+        void 기준개수가_아니면_생성안함() {
+            RunnectUser user = buildUser(1L);
+            for (int i = 0; i < 5; i++) {
+                user.updateCreatedCourse();
+            }
+
+            userStampService.createStampByUser(user, StampType.c);
+
+            verify(userStampRepository, never()).save(any());
+        }
+
+        @Test
+        @DisplayName("스크랩 타입(s)은 createdScrap 기준으로 판단한다")
+        void 스크랩_타입() {
+            RunnectUser user = buildUser(1L);
+            user.updateCreatedScrap();
+
+            userStampService.createStampByUser(user, StampType.s);
+
+            org.mockito.ArgumentCaptor<UserStamp> captor = org.mockito.ArgumentCaptor.forClass(UserStamp.class);
+            verify(userStampRepository).save(captor.capture());
+            assertThat(captor.getValue().getStampId()).isEqualTo(StampType.s1);
+        }
+
+        @Test
+        @DisplayName("기록 타입(r)은 createdRecord 기준으로 판단한다")
+        void 기록_타입() {
+            RunnectUser user = buildUser(1L);
+            user.updateCreatedRecord();
+
+            userStampService.createStampByUser(user, StampType.r);
+
+            org.mockito.ArgumentCaptor<UserStamp> captor = org.mockito.ArgumentCaptor.forClass(UserStamp.class);
+            verify(userStampRepository).save(captor.capture());
+            assertThat(captor.getValue().getStampId()).isEqualTo(StampType.r1);
+        }
+
+        @Test
+        @DisplayName("업로드 타입(u)은 createdPublicCourse 기준으로 판단한다")
+        void 업로드_타입() {
+            RunnectUser user = buildUser(1L);
+            user.updateCreatedPublicCourse();
+
+            userStampService.createStampByUser(user, StampType.u);
+
+            org.mockito.ArgumentCaptor<UserStamp> captor = org.mockito.ArgumentCaptor.forClass(UserStamp.class);
+            verify(userStampRepository).save(captor.capture());
+            assertThat(captor.getValue().getStampId()).isEqualTo(StampType.u1);
+        }
+
+        @Test
+        @DisplayName("[설계상 주의] 이미 레벨이 붙은 타입(c1 등)으로 호출하면 조용히 무시된다")
+        void 레벨_붙은_타입으로_호출하면_무시됨() {
+            RunnectUser user = buildUser(1L);
+            user.updateCreatedCourse();
+
+            userStampService.createStampByUser(user, StampType.c1);
+
+            verify(userStampRepository, never()).save(any());
+        }
+
+        @Test
+        @DisplayName("누적 스탬프 개수가 4의 배수(12 이하)가 되면 레벨업한다")
+        void 스탬프_4개면_레벨업() {
+            RunnectUser user = buildUser(1L);
+            user.updateCreatedCourse();
+            when(userStampRepository.countByRunnectUser(user)).thenReturn(4L);
+
+            userStampService.createStampByUser(user, StampType.c);
+
+            assertThat(user.getLevel()).isEqualTo(2);
+        }
+
+        @Test
+        @DisplayName("누적 스탬프 개수가 8이면 레벨 3이 된다")
+        void 스탬프_8개면_레벨3() {
+            RunnectUser user = buildUser(1L);
+            user.updateCreatedCourse();
+            when(userStampRepository.countByRunnectUser(user)).thenReturn(8L);
+
+            userStampService.createStampByUser(user, StampType.c);
+
+            assertThat(user.getLevel()).isEqualTo(3);
+        }
+
+        @Test
+        @DisplayName("누적 스탬프 개수가 12를 넘으면 더 이상 레벨업하지 않는다")
+        void 스탬프_12_초과면_레벨업_안함() {
+            RunnectUser user = buildUser(1L);
+            user.updateCreatedCourse();
+            int levelBefore = user.getLevel();
+            when(userStampRepository.countByRunnectUser(user)).thenReturn(16L);
+
+            userStampService.createStampByUser(user, StampType.c);
+
+            assertThat(user.getLevel()).isEqualTo(levelBefore);
+        }
+
+        @Test
+        @DisplayName("스탬프 개수가 4의 배수가 아니면 레벨업하지 않는다")
+        void 배수가_아니면_레벨업_안함() {
+            RunnectUser user = buildUser(1L);
+            user.updateCreatedCourse();
+            int levelBefore = user.getLevel();
+            when(userStampRepository.countByRunnectUser(user)).thenReturn(5L);
+
+            userStampService.createStampByUser(user, StampType.c);
+
+            assertThat(user.getLevel()).isEqualTo(levelBefore);
+        }
+    }
+
+    @Nested
+    @DisplayName("findUserStamps")
+    class FindUserStamps {
+
+        @Test
+        @DisplayName("정상 조회 시 유저의 스탬프 목록을 반환한다")
+        void 정상_조회() {
+            RunnectUser user = buildUser(1L);
+            when(userRepository.findUserByIdWithUserStamps(1L)).thenReturn(Optional.of(user));
+
+            GetUserStampsResponseDto response = userStampService.findUserStamps(1L);
+
+            // GetUserStampsResponseDto.UserInfo/StampInfo는 private static class라
+            // 외부(테스트)에서 타입을 직접 다룰 수 없어 리플렉션으로 필드를 확인한다.
+            Object userInfo = ReflectionTestUtils.invokeMethod(response, "getUser");
+            assertThat(ReflectionTestUtils.getField(userInfo, "id")).isEqualTo(1L);
+            assertThat(response.getStamps()).isEmpty();
+        }
+
+        @Test
+        @DisplayName("존재하지 않는 유저면 NotFoundUserException")
+        void 존재하지_않는_유저() {
+            when(userRepository.findUserByIdWithUserStamps(1L)).thenReturn(Optional.empty());
+
+            assertThatThrownBy(() -> userStampService.findUserStamps(1L))
+                .isInstanceOf(NotFoundUserException.class);
+        }
+    }
+}