A semiconductor laser diode includes, on a substrate, a first cladding layer; an active layer formed on the first cladding layer; a second cladding layer formed on the active layer and having a ridge stripe for injecting a current into the active layer; and a light emitting portion formed on both sides of the ridge stripe and having a current blocking layer for confining the current in the ridge stripe. A distance from a lower face of the current blocking layer to an upper face of the active layer is within a given range. Also, the current spreads beyond a width of the ridge stripe after passing the ridge stripe and before reaching the active layer.