An active layer in which laser light is generated by injecting driving current therein is sandwiched between semiconductor layers. The active layer has a multi-quantum-well structure, and the layers located at both sides of the active layer are made of an AlGaAs-based material. Refractive indices of the layers are set asymmetrically with respect to the active layer by properly selecting aluminum-mixing ratios in AlGa. Since the light generated in the active layer is distributed more in a layer having a higher refractive index, a peak of the light distribution is shifted from the active layer into the layer having a higher refractive index. Thus, energy concentration to the active layer is avoided. A thickness of the layer having a higher refractive index may be made thicker to further enhance the energy concentration shift from the active layer.