A semiconductor laser includes semiconductor layers stacked on a substrate, and a pair of resonator end surfaces opposed to each other in the direction perpendicular to the stacking direction. In this semiconductor laser, a light emission side reflecting film is formed on one of the resonator end surfaces. A refractive index of the reflecting film against an emission wavelength of laser light is set to a value between an effective refractive index and a refractive index of the substrate. Another semiconductor laser includes a light emission function layer stack including a cladding layer and an active layer formed on one place of a translucent substrate; two electrodes having different polarities, which are provided on the light emission function layer stack side; and a light leakage preventive film formed on the other plane of the translucent substrate.