A semiconductor laser device comprises a cladding layer of a first conductivity type, an active layer, a cladding layer of a second conductivity type, and a current blocking layer having a stripe-shaped opening having a predetermined width W for restricting a current path and forming the current path, and having a larger band gap than that of the cladding layer of the second conductivity type and having a smaller refractive index than that of the cladding layer of the second conductivity type. A difference .DELTA.n between effective refractive indexes in a region, which corresponds to the opening, in the active layer and an effective refractive index in a region, which corresponds to both sides of the opening, in the active layer and the width W (.mu.m) of the opening are so set as to satisfy a predetermined relationship. The difference .DELTA.n between the effective refractive indexes is set by selecting the A1 composition ratio of the current blocking layer and the thickness of the cladding layer of the second conductivity type on the both sides of the opening.