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 24178915..9cc9e503 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
@@ -22,6 +22,7 @@ public interface FileManager {
     void removeFile(String fileName);
 
     boolean isExist(Path path);
+    boolean isExist(String fileName);
 
     void autoCreateDir(Path path);
 
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 63bfc3c1..4abdc172 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
@@ -54,6 +54,17 @@ public class FileManagerImpl implements FileManager {
         this.currentDir = rootDir.resolve(dirName);
     }
 
+    @Override
+    public void changeDir(Path path) {
+        if (path.startsWith(rootDir)) {
+            this.currentDir = path;
+        }
+        else {
+            logger.debug("changeDir", "invalid path: " + path);
+            // TODO-rca: 例外を投げる
+        }
+    }
+
     @Override
     public void backDir() {
         this.currentDir = currentDir.getParent();
@@ -115,6 +126,12 @@ public class FileManagerImpl implements FileManager {
         return Files.exists(path);
     }
 
+    @Override
+    public boolean isExist(String fileName) {
+        logger.debug("isExist", "called");
+        return Files.exists(currentDir.resolve(fileName));
+    }
+
     @Override
     public void autoCreateDir(Path path) {
         logger.debug("autoCreateDir", "called");