PURPOSE: To easily manufacture a semiconductor laser and to protect the end face of the laser against damage when it outputs laser of high power by a method wherein the part of the well layer of an active layer near both the end faces is set thinner than the other pat of the well layer.

CONSTITUTION: The well layer 38 of an active layer 32 close to an end face is set thinner than the well layer 36 of an inner active layer 31. In an active layer of quantum well structure, when a well layer is reduced to a thickness of below 200, a phenomenon that an active layer is enhanced in band gap energy due to a quantum effect takes place. As the thickness of the well layer 38 of the active layer 32 near the end face is set 10% smaller than that of the well layer 36 of the inner active layer 31, the active layer 32 becomes larger than the active layer 31 in band gap energy due to a quantum effect. Therefore, laser rays generated inside the active layer 31 are hardly absorbed by the active layer 32, so that an end face can outputted.