diff --git a/src/renderer/inbox/components/SearchBox.tsx b/src/renderer/inbox/components/SearchBox.tsx
index 2de58a8..bfebff8 100644
--- a/src/renderer/inbox/components/SearchBox.tsx
+++ b/src/renderer/inbox/components/SearchBox.tsx
@@ -3,32 +3,50 @@ import { useInbox } from '../store.js';
 
 export function SearchBox(): React.ReactElement {
   const [draft, setDraft] = useState('');
+  const [scope, setScope] = useState<'current' | 'all'>('current');
+  const selectedNotebookId = useInbox((s) => s.selectedNotebookId);
 
   useEffect(() => {
     const handle = setTimeout(() => {
       const trimmed = draft.trim();
-      if (trimmed.length === 0) useInbox.getState().clearSearch();
-      else void useInbox.getState().searchNotes(trimmed);
+      if (trimmed.length === 0) {
+        useInbox.getState().clearSearch();
+      } else {
+        // v0.4 Task 18 — scope='current' 이면 현재 notebook ID 전달, 'all' 이면 미전달(전체 검색).
+        const notebookId = scope === 'current' ? (selectedNotebookId ?? undefined) : undefined;
+        void useInbox.getState().searchNotes(trimmed, { notebookId });
+      }
     }, 200);
     return () => clearTimeout(handle);
-  }, [draft]);
+  }, [draft, scope, selectedNotebookId]);
 
   return (
-    <input
-      type="search"
-      role="searchbox"
-      placeholder="검색…"
-      value={draft}
-      onChange={(e) => setDraft(e.target.value)}
-      aria-label="노트 검색"
-      style={{
-        marginLeft: 12,
-        padding: '4px 8px',
-        fontSize: 12,
-        border: '1px solid #bbb',
-        borderRadius: 4,
-        width: 200
-      }}
-    />
+    <span style={{ display: 'inline-flex', alignItems: 'center' }}>
+      <input
+        type="search"
+        role="searchbox"
+        placeholder="검색…"
+        value={draft}
+        onChange={(e) => setDraft(e.target.value)}
+        aria-label="노트 검색"
+        style={{
+          marginLeft: 12,
+          padding: '4px 8px',
+          fontSize: 12,
+          border: '1px solid #bbb',
+          borderRadius: 4,
+          width: 200
+        }}
+      />
+      <select
+        value={scope}
+        onChange={(e) => setScope(e.target.value as 'current' | 'all')}
+        aria-label="검색 범위"
+        style={{ fontSize: 11, padding: '2px 4px', marginLeft: 4 }}
+      >
+        <option value="current">이 노트북</option>
+        <option value="all">모든 노트북</option>
+      </select>
+    </span>
   );
 }
diff --git a/src/renderer/inbox/store.ts b/src/renderer/inbox/store.ts
index 601b230..eb12e60 100644
--- a/src/renderer/inbox/store.ts
+++ b/src/renderer/inbox/store.ts
@@ -1,5 +1,5 @@
 import { create } from 'zustand';
-import type { Note, Notebook, PromotionCandidate, ReviewAggregate, WeeklyContinuity } from '@shared/types';
+import type { Note, NoteStatus, Notebook, PromotionCandidate, ReviewAggregate, WeeklyContinuity } from '@shared/types';
 import { inboxApi, notebookApi } from './api.js';
 import { nextKstMidnightMs } from '@shared/util/kstDate.js';
 
@@ -79,7 +79,8 @@ interface InboxState {
   snoozeRecall: () => Promise<void>;
   // v0.2.11 Cut D — search + review actions.
   setSearchQuery: (q: string) => void;
-  searchNotes: (q: string) => Promise<void>;
+  // v0.4 Task 18 — scope 토글. notebookId 전달 시 해당 notebook 안 검색, undefined 시 전체 검색.
+  searchNotes: (q: string, opts?: { notebookId?: string }) => Promise<void>;
   clearSearch: () => void;
   loadReview: (period: 'daily' | 'weekly' | 'monthly') => Promise<void>;
   // v0.4 — Notebook actions.
@@ -383,7 +384,7 @@ export const useInbox = create<InboxState>((set, get) => ({
     set({ searchQuery: q });
     if (q.trim().length === 0) set({ searchResults: null });
   },
-  async searchNotes(q) {
+  async searchNotes(q, opts) {
     if (q.trim().length === 0) {
       set({ searchResults: null });
       return;
@@ -394,7 +395,10 @@ export const useInbox = create<InboxState>((set, get) => ({
       ? (view === 'trash' ? 'trashed' : view)
       : view === 'inbox' ? 'active' : undefined;
     try {
-      const r = await inboxApi.search(q, status ? { status } : {});
+      // v0.4 Task 18 — opts.notebookId 전달 시 해당 notebook 안 검색, undefined 시 전체 검색.
+      const searchOpts: { status?: NoteStatus; notebookId?: string } = status ? { status: status as NoteStatus } : {};
+      if (opts?.notebookId !== undefined) searchOpts.notebookId = opts.notebookId;
+      const r = await inboxApi.search(q, searchOpts);
       set({ searchResults: r });
     } catch (e) {
       // FTS5 query parse error (special char 미escape) / IPC fail → 빈 결과로.
diff --git a/tests/unit/SearchBox.test.tsx b/tests/unit/SearchBox.test.tsx
index 9292ae7..92b1b9c 100644
--- a/tests/unit/SearchBox.test.tsx
+++ b/tests/unit/SearchBox.test.tsx
@@ -9,10 +9,13 @@ const { mockSearchNotes, mockClearSearch } = vi.hoisted(() => ({
   mockClearSearch: vi.fn()
 }));
 
+// selectedNotebookId 를 테스트 간 변경할 수 있도록 ref 로 관리.
+let mockSelectedNotebookId: string | null = 'nb-1';
+
 vi.mock('../../src/renderer/inbox/store.js', () => ({
   useInbox: Object.assign(
-    (selector?: (s: { searchQuery: string }) => unknown) => {
-      const state = { searchQuery: '' };
+    (selector?: (s: { searchQuery: string; selectedNotebookId: string | null }) => unknown) => {
+      const state = { searchQuery: '', selectedNotebookId: mockSelectedNotebookId };
       return selector ? selector(state) : state;
     },
     { getState: () => ({ searchNotes: mockSearchNotes, clearSearch: mockClearSearch }) }
@@ -26,6 +29,7 @@ describe('SearchBox', () => {
     vi.clearAllMocks();
     cleanup();
     vi.useFakeTimers();
+    mockSelectedNotebookId = 'nb-1';
   });
 
   it('타이핑 → 200ms debounce 후 searchNotes 호출', () => {
@@ -34,7 +38,7 @@ describe('SearchBox', () => {
     fireEvent.change(input, { target: { value: '회의' } });
     expect(mockSearchNotes).not.toHaveBeenCalled();
     vi.advanceTimersByTime(200);
-    expect(mockSearchNotes).toHaveBeenCalledWith('회의');
+    expect(mockSearchNotes).toHaveBeenCalledWith('회의', { notebookId: 'nb-1' });
   });
 
   it('빈 값 → clearSearch 호출', () => {
@@ -44,4 +48,32 @@ describe('SearchBox', () => {
     vi.advanceTimersByTime(200);
     expect(mockClearSearch).toHaveBeenCalled();
   });
+
+  it('기본 scope=current — searchNotes 에 selectedNotebookId 전달', () => {
+    render(<SearchBox />);
+    const input = screen.getByRole('searchbox');
+    fireEvent.change(input, { target: { value: '노트' } });
+    vi.advanceTimersByTime(200);
+    expect(mockSearchNotes).toHaveBeenCalledWith('노트', { notebookId: 'nb-1' });
+  });
+
+  it('scope=all 변경 시 다음 검색에서 notebookId 미전달 (undefined)', () => {
+    render(<SearchBox />);
+    const input = screen.getByRole('searchbox');
+    const scopeSelect = screen.getByRole('combobox', { name: '검색 범위' });
+
+    fireEvent.change(scopeSelect, { target: { value: 'all' } });
+    fireEvent.change(input, { target: { value: '리뷰' } });
+    vi.advanceTimersByTime(200);
+    expect(mockSearchNotes).toHaveBeenCalledWith('리뷰', { notebookId: undefined });
+  });
+
+  it('selectedNotebookId=null 이면 scope=current 에서 notebookId=undefined 전달', () => {
+    mockSelectedNotebookId = null;
+    render(<SearchBox />);
+    const input = screen.getByRole('searchbox');
+    fireEvent.change(input, { target: { value: '테스트' } });
+    vi.advanceTimersByTime(200);
+    expect(mockSearchNotes).toHaveBeenCalledWith('테스트', { notebookId: undefined });
+  });
 });