The ridge semiconductor laser is a semiconductor laser in which a carrier stopper layer made of an AlInAs compound, a clad layer made of an AlGaInAs compound, and an etching stopper layer made of an InGaAsP compound are stacked in sequence on one side of an active layer made of an AlGaInAs compound. The ridge semiconductor laser is provided with a ridge waveguide including, in a layer made of an InP compound, a diffraction grating made of an InGaAsP compound on the opposite side of the clad layer of the etching stopper layer.