diff --git a/.gitignore b/.gitignore
index eba74f4..2f1494f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-venv/
\ No newline at end of file
+venv/
+__pycache__
\ No newline at end of file
diff --git a/example/debug.py b/example/debug.py
new file mode 100644
index 0000000..57ae8ac
--- /dev/null
+++ b/example/debug.py
@@ -0,0 +1,19 @@
+import sys
+import os
+sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "src")))
+
+from libs.custom_logger import get_logger
+from libs.time_watch import TimeWatch
+
+# level = 10  # DEBUG level
+logger = get_logger(level=10)
+logger.debug("Debug message")
+
+@TimeWatch.debug(logger=logger)
+def app_run():
+    import time
+    time.sleep(2)
+    return "Function executed."
+
+if __name__ == "__main__":
+    app_run()
diff --git a/src/libs/__init__.py b/src/libs/__init__.py
new file mode 100644
index 0000000..2a9a790
--- /dev/null
+++ b/src/libs/__init__.py
@@ -0,0 +1,11 @@
+from .custom_logger import get_logger, CustomLogger
+from .time_watch import TimeWatch
+from .singleton import Singleton
+
+__all__ = [
+    "get_logger",
+    "CustomLogger",
+    "TimeWatch",
+    "Singleton",
+]
+
diff --git a/src/libs/custom_logger.py b/src/libs/custom_logger.py
new file mode 100644
index 0000000..48e219e
--- /dev/null
+++ b/src/libs/custom_logger.py
@@ -0,0 +1,48 @@
+import logging
+import functools
+from .singleton import Singleton
+
+class CustomLogger(Singleton):
+    def __init__(self, name='main', log_file=None, level=logging.INFO):
+        if hasattr(self, '_initialized') and self._initialized:
+            self.logger.setLevel(level)
+            return  # すでに初期化済みなら何もしない
+
+        self.logger = logging.getLogger(name)
+        self.logger.setLevel(level)
+        self.logger.propagate = False
+
+        formatter = logging.Formatter(
+            '%(asctime)s %(levelname)s [%(filename)s:%(lineno)3d]: %(message)s'
+        )
+
+        # Console handler
+        ch = logging.StreamHandler()
+        ch.setFormatter(formatter)
+        self.logger.addHandler(ch)
+
+        # File handler
+        if log_file:
+            fh = logging.FileHandler(log_file, encoding='utf-8')
+            fh.setFormatter(formatter)
+            self.logger.addHandler(fh)
+
+        self._initialized = True
+
+
+    def get_logger(self):
+        return self.logger
+
+    def log_entry_exit(self, func):
+        @functools.wraps(func)
+        def wrapper(*args, **kwargs):
+            self.logger.info(f"Enter: {func.__qualname__}")
+            result = func(*args, **kwargs)
+            self.logger.info(f"Exit: {func.__qualname__}")
+            return result
+        return wrapper
+
+
+def get_logger(name='main', log_file=None, level=logging.INFO):
+    custom_logger = CustomLogger(name, log_file, level)
+    return custom_logger.get_logger()
diff --git a/src/libs/singleton.py b/src/libs/singleton.py
new file mode 100644
index 0000000..2313286
--- /dev/null
+++ b/src/libs/singleton.py
@@ -0,0 +1,20 @@
+"""Singleton pattern implementation in Python.
+This implementation is thread-safe and ensures that only one instance of the class is created.
+
+Singleton が提供するのは「同じインスタンスを返す仕組み」
+* __init__() は毎回呼ばれる（多くの人が意図しない動作）
+* __init__の2回目は_initialized というフラグは 使う側で管理する必要がある。
+"""
+
+import threading
+
+class Singleton(object):
+    _instances = {}
+    _lock = threading.Lock()
+
+    def __new__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            with cls._lock:
+                if cls not in cls._instances:  # ダブルチェック
+                    cls._instances[cls] = super(Singleton, cls).__new__(cls)
+        return cls._instances[cls]
diff --git a/src/libs/time_watcg.py b/src/libs/time_watch.py
similarity index 68%
rename from src/libs/time_watcg.py
rename to src/libs/time_watch.py
index 7933e1a..39f359c 100644
--- a/src/libs/time_watcg.py
+++ b/src/libs/time_watch.py
@@ -36,20 +36,22 @@ class TimeWatch:
         self.end_time = None
         self.logger.debug("Timer reset.")
 
-    @classmethod
-    def debug(cls, func):
-        def wrapper(*args, **kwargs):
-            instance = cls()    # インスタンスを作成
-            instance.start()
-            result = func(*args, **kwargs)
-            instance.stop()
-            instance.elapsed_time()
-            return result
-        return wrapper
+    @staticmethod
+    def debug(logger=None):
+        def decorator(func):
+            def wrapper(*args, **kwargs):
+                timer = TimeWatch(logger=logger)
+                timer.start()
+                result = func(*args, **kwargs)
+                timer.stop()
+                timer.elapsed_time()
+                return result
+            return wrapper
+        return decorator
 
 
 if __name__ == "__main__":
-    @TimeWatch.debug
+    @TimeWatch.debug()
     def test_function():
         time.sleep(2)
         return "Function executed."