There is provided a semiconductor laser comprising an n-InP substrate 1; a multilayer film including a strained MQW active layer 6 on the n-InP substrate 1; a p-electrode 18 on the multilayer film; a pair of grooves 15 separating the multilayer film in both edges of the p-electrode 18 and extending to the n-InP substrate 1; and a plurality of diffraction gratings formed in an area from one to the other of the pair of grooves 15 in a diffraction grating forming surface formed in the upper surface of the n-InP substrate 1 or the upper surface of any of the semiconductor films in the multilayer film.