A semiconductor laser device comprises an n-type cladding layer 103 made of n.sup.-type (Al.sub.0.3Ga.sub.0.7).sub.0.5In.sub.0.5P, an undoped active layer 104 and a first p-type cladding layer 105 made of p.sup.-type (Al.sub.0.3Ga.sub.0.7).sub.0.5In.sub.0.5P. These layers are successively stacked in bottom-to-top order. The active layer 104 has a multi-quantum well structure composed of a first optical guide layer of undoped Al.sub.0.4Ga.sub.0.6As, a layered structure in which well layers of undoped GaAs and barrier layers of undoped Al.sub.0.4Ga.sub.0.6As are alternately formed, and a second optical guide layer of undoped Al.sub.0.4Ga.sub.0.6As. The first optical guide layer, the layered structure and the second optical guide layer are successively stacked in bottom-to-top order.