diff --git a/src/main/java/app/nook/focus/converter/FocusConverter.java b/src/main/java/app/nook/focus/converter/FocusConverter.java
index ce5cd5c..bff4d08 100644
--- a/src/main/java/app/nook/focus/converter/FocusConverter.java
+++ b/src/main/java/app/nook/focus/converter/FocusConverter.java
@@ -3,6 +3,7 @@
 import app.nook.focus.domain.Focus;
 import app.nook.focus.domain.Theme;
 import app.nook.focus.dto.FocusResponseDto;
+import app.nook.library.util.FocusTimeUtil;
 
 import java.util.List;
 
@@ -40,7 +41,7 @@ public static FocusResponseDto.FocusEnd toFocusEndResponse(Focus focus) {
                 focus.getStartedAt(),
                 focus.getEndedAt(),
                 focus.getDurationSec(),
-                formatDuration(focus.getDurationSec()),
+                FocusTimeUtil.formatFocusTime(focus.getDurationSec() == null ? 0 : focus.getDurationSec()),
                 focus.getLibrary().getPage(),
                 focus.getLibrary().getFocusSec(),
                 focus.getLibrary().getReadingStatus().name()
@@ -50,27 +51,13 @@ public static FocusResponseDto.FocusEnd toFocusEndResponse(Focus focus) {
     public static FocusResponseDto.RecentFocusItem toRecentFocusItem(Focus focus, String coverImageUrl) {
         return new FocusResponseDto.RecentFocusItem(
                 focus.getId(),
-                focus.getLibrary().getId(),
                 focus.getLibrary().getBook().getId(),
                 focus.getLibrary().getBook().getTitle(),
                 focus.getLibrary().getBook().getAuthor(),
                 coverImageUrl,
                 focus.getStartedAt(),
                 focus.getEndedAt(),
-                focus.getDurationSec(),
-                formatDuration(focus.getDurationSec())
+                FocusTimeUtil.formatFocusTime(focus.getDurationSec() == null ? 0 : focus.getDurationSec())
         );
     }
-
-    private static String formatDuration(Integer totalSec) {
-        if (totalSec == null) {
-            return "00:00:00";
-        }
-
-        int hour = totalSec / 3600;
-        int minute = (totalSec % 3600) / 60;
-        int second = totalSec % 60;
-
-        return String.format("%02d:%02d:%02d", hour, minute, second);
-    }
 }
diff --git a/src/main/java/app/nook/focus/dto/FocusResponseDto.java b/src/main/java/app/nook/focus/dto/FocusResponseDto.java
index e6ee40c..4e57ea0 100644
--- a/src/main/java/app/nook/focus/dto/FocusResponseDto.java
+++ b/src/main/java/app/nook/focus/dto/FocusResponseDto.java
@@ -41,14 +41,12 @@ public record FocusEnd(
 
     public record RecentFocusItem(
             Long focusId,
-            Long libraryId,
             Long bookId,
             String bookTitle,
             String author,
             String coverImageUrl,
             LocalDateTime startedAt,
             LocalDateTime endedAt,
-            Integer durationSec,
             String durationText
     ) {}
 }
diff --git a/src/test/java/app/nook/controller/focus/FocusControllerTest.java b/src/test/java/app/nook/controller/focus/FocusControllerTest.java
index 8dc0668..22eebc3 100644
--- a/src/test/java/app/nook/controller/focus/FocusControllerTest.java
+++ b/src/test/java/app/nook/controller/focus/FocusControllerTest.java
@@ -228,14 +228,12 @@ class GetRecentFocuses {
                     List.of(
                             new FocusResponseDto.RecentFocusItem(
                                     100L,
-                                    10L,
                                     20L,
                                     "첫사랑의 침공",
                                     "권혁일",
                                     "https://cdn.nook.com/covers/book.jpg",
                                     LocalDateTime.of(2026, 3, 22, 14, 0, 0),
                                     LocalDateTime.of(2026, 3, 22, 14, 34, 26),
-                                    2066,
                                     "00:34:26"
                             )
                     ),
@@ -262,14 +260,12 @@ class GetRecentFocuses {
                                     ApiResponseSnippet.withResult(
                                             fieldWithPath("result.items[]").type(ARRAY).description("포커스 목록"),
                                             fieldWithPath("result.items[].focusId").type(NUMBER).description("포커스 ID"),
-                                            fieldWithPath("result.items[].libraryId").type(NUMBER).description("서재 ID"),
                                             fieldWithPath("result.items[].bookId").type(NUMBER).description("책 ID"),
                                             fieldWithPath("result.items[].bookTitle").type(STRING).description("책 제목"),
                                             fieldWithPath("result.items[].author").type(STRING).description("저자"),
                                             fieldWithPath("result.items[].coverImageUrl").type(STRING).description("책 커버 이미지 URL"),
                                             fieldWithPath("result.items[].startedAt").type(STRING).description("포커스 시작 시각"),
                                             fieldWithPath("result.items[].endedAt").type(STRING).description("포커스 종료 시각"),
-                                            fieldWithPath("result.items[].durationSec").type(NUMBER).description("집중 시간(초)"),
                                             fieldWithPath("result.items[].durationText").type(STRING).description("집중 시간(HH:mm:ss)"),
                                             fieldWithPath("result.nextCursor").type(NUMBER).optional().description("다음 커서 (다음 페이지 없으면 null)"),
                                             fieldWithPath("result.hasNext").type(BOOLEAN).description("다음 페이지 존재 여부")
diff --git a/src/test/java/app/nook/focus/service/FocusQueryServiceTest.java b/src/test/java/app/nook/focus/service/FocusQueryServiceTest.java
index 68d848e..fec7a1c 100644
--- a/src/test/java/app/nook/focus/service/FocusQueryServiceTest.java
+++ b/src/test/java/app/nook/focus/service/FocusQueryServiceTest.java
@@ -80,10 +80,8 @@ class GetRecentFocuses {
 
             FocusResponseDto.RecentFocusItem item = result.getItems().get(0);
             assertThat(item.focusId()).isEqualTo(completedFocus.getId());
-            assertThat(item.libraryId()).isEqualTo(library.getId());
             assertThat(item.bookId()).isEqualTo(library.getBook().getId());
             assertThat(item.coverImageUrl()).isEqualTo("https://cdn.nook.com/covers/book.jpg");
-            assertThat(item.durationSec()).isEqualTo(2066);
             assertThat(item.durationText()).isEqualTo("00:34:26");
         }