<p>A nitride semiconductor device is composed of a III nitride semiconductor and has a semiconductor laminated body (50), which has a light emitting end surface, and a first coat film (23), which is formed to cover the light emitting end surface of the semiconductor laminated body (50). The first coat film (23) is a crystalline film composed of a nitride which contains aluminum. The crystalline film is composed of an assembly of a plurality of domains having the same tilt angle and rotation angle of the crystalline orientation plane, and the length of the boundary of each domain per unit area is 7 µm-1 or shorter.</p>
