Provided is a semiconductor laser including: a substrate (semiconductor substrate); an optical waveguide (active layer waveguide) with a mesa structure that includes an active layer (strain-compensated multiple quantum well active layer) including Al, is provided over the semiconductor substrate; a semiconductor protective layer that is provided so as to cover the top and the side of a mesa of the active layer waveguide; a current block layer that is provided so as to embed the active layer waveguide and the semiconductor protective layer; and a clad layer (p-type InP clad layer) that is provided over the semiconductor protective layer and the current block layer, wherein, the semiconductor protective layer has a semiconductor layer (p-type InGaAsP protective layer) that includes As, but does not include Al.