Abstract: A nitride semiconductor device having high electrode contact properties is disclosed. The nitride semiconductor device includes a semiconductor layer made of a group III nitride semiconductor, and a metal electrode for supplying the semiconductor layer with a carrier. The device has a first contact layer made of a group III nitride semiconductor (AlxGa1−x)1−yInyN (0≦x≦1, 0<y≦1), laminated between the semiconductor layer and the metal electrode, and a group II element added thereto, and a second contact layer made of a group III nitride semiconductor Alx′Ga1−x′N (0≦x′≦1) and laminated between the first contact and the metal electrode.