diff --git a/frontend/book-editor.html b/frontend/book-editor.html
index a065216..6a86ed6 100644
--- a/frontend/book-editor.html
+++ b/frontend/book-editor.html
@@ -150,7 +150,7 @@
                                             <select x-model="doc.matched_pdf_id" 
                                                     :class="doc.matched_pdf_id ? 'border-green-300 bg-green-50' : 'border-gray-300'"
                                                     class="w-full px-3 py-2 rounded-lg focus:ring-2 focus:ring-blue-500 focus:border-transparent text-sm">
-                                                <option :value="null">PDF 매칭 없음</option>
+                                                <option value="">PDF 매칭 없음</option>
                                                 <template x-for="pdf in availablePDFs" :key="pdf.id">
                                                     <option :value="pdf.id" x-text="pdf.title"></option>
                                                 </template>
diff --git a/frontend/static/js/book-editor.js b/frontend/static/js/book-editor.js
index 8aa18d1..fd3b423 100644
--- a/frontend/static/js/book-editor.js
+++ b/frontend/static/js/book-editor.js
@@ -95,6 +95,11 @@ window.bookEditorApp = () => ({
                 console.log(`📄 문서 ${index + 1}: ${doc.title}`);
                 console.log(`  - matched_pdf_id: ${doc.matched_pdf_id || 'null'}`);
                 console.log(`  - sort_order: ${doc.sort_order || 'null'}`);
+                
+                // null 값을 빈 문자열로 변환 (UI 바인딩을 위해)
+                if (doc.matched_pdf_id === null) {
+                    doc.matched_pdf_id = "";
+                }
             });
             
             // 사용 가능한 PDF 문서들 로드 (현재 서적의 PDF만)
@@ -237,7 +242,7 @@ window.bookEditorApp = () => ({
                 
                 return window.api.updateDocument(doc.id, {
                     sort_order: doc.sort_order,
-                    matched_pdf_id: doc.matched_pdf_id === "" ? null : doc.matched_pdf_id
+                    matched_pdf_id: doc.matched_pdf_id === "" || doc.matched_pdf_id === null ? null : doc.matched_pdf_id
                 });
             });