diff --git a/source/src/main/java/one/nem/lacerta/source/file/FileManager.java b/source/src/main/java/one/nem/lacerta/source/file/FileManager.java
index aaf78c1c..c1488183 100644
--- a/source/src/main/java/one/nem/lacerta/source/file/FileManager.java
+++ b/source/src/main/java/one/nem/lacerta/source/file/FileManager.java
@@ -34,12 +34,12 @@ public interface FileManager {
 
     // Save
     // XML
-    FileManager saveXml(Document document, String fileName) throws IOException;
-    FileManager saveXml(Document document) throws IOException;
+    void saveXml(Document document, String fileName) throws IOException;
+    void saveXml(Document document) throws IOException;
 
     // Bitmap
-    FileManager saveBitmap(Bitmap bitmap, String fileName) throws IOException; // TODO-rca: パラメータに対応させる
-    FileManager saveBitmap(Bitmap bitmap) throws IOException; // TODO-rca: パラメータに対応させる
+    void saveBitmap(Bitmap bitmap, String fileName) throws IOException; // TODO-rca: パラメータに対応させる
+    void saveBitmap(Bitmap bitmap) throws IOException; // TODO-rca: パラメータに対応させる
 
 
     // Load
diff --git a/source/src/main/java/one/nem/lacerta/source/file/impl/FileManagerImpl.java b/source/src/main/java/one/nem/lacerta/source/file/impl/FileManagerImpl.java
index 799a0851..5cf0eb10 100644
--- a/source/src/main/java/one/nem/lacerta/source/file/impl/FileManagerImpl.java
+++ b/source/src/main/java/one/nem/lacerta/source/file/impl/FileManagerImpl.java
@@ -187,22 +187,22 @@ public class FileManagerImpl implements FileManager {
     }
 
     @Override
-    public FileManager saveXml(Document document, String fileName) throws IOException {
+    public void saveXml(Document document, String fileName) throws IOException {
         return null;
     }
 
     @Override
-    public FileManager saveXml(Document document) throws IOException {
+    public void saveXml(Document document) throws IOException {
         return null;
     }
 
     @Override
-    public FileManager saveBitmap(Bitmap bitmap, String fileName) throws IOException {
+    public void saveBitmap(Bitmap bitmap, String fileName) throws IOException {
         return null;
     }
 
     @Override
-    public FileManager saveBitmap(Bitmap bitmap) throws IOException {
+    public void saveBitmap(Bitmap bitmap) throws IOException {
         return null;
     }