A nitride semiconductor device of the self-pulsation type comprises as superposed on a substrate 1 an n-type cladding layer 3, active layer 4 and p-type cladding layer including an upwardly projecting stripe portion 53, an n-type current blocking layer 6 being formed at each of opposite sides of the stripe portion 53. The stripe portion 53 of the p-type cladding layer 5 comprises an upper stripe portion 51 and a lower stripe portion 52. The upper stripe portion 51 has a minimum width W1 at the position of the boundary between the upper and lower stripe portions 51, 52, and the lower stripe portion 52 has at the position of its lower end a width W2 greater than the minimum width W1 of the upper stripe portion 51. This construction realizes a higher yield than in the prior art.