diff --git a/src/calculator.py b/src/calculator.py
index 1292e98..db09d50 100644
--- a/src/calculator.py
+++ b/src/calculator.py
@@ -8,3 +8,8 @@ def divide(a: int, b: int) -> float:
     if b == 0:
         raise ValueError("除數不能為 0")
     return a / b
+
+
+def multiply(a: int, b: int) -> int:
+    """兩數相乘"""
+    return a * b
diff --git a/tests/test_calculator.py b/tests/test_calculator.py
index 4365313..4e0aed2 100644
--- a/tests/test_calculator.py
+++ b/tests/test_calculator.py
@@ -1,6 +1,6 @@
 import pytest
 
-from src.calculator import add, divide
+from src.calculator import add, divide, multiply
 
 
 def test_add():
@@ -14,3 +14,7 @@ def test_divide():
 def test_divide_by_zero():
     with pytest.raises(ValueError):
         divide(1, 0)
+
+
+def test_multiply():
+    assert multiply(2, 3) == 6