A semiconductor laser device includes: an n-type cladding layer, an active layer, and a p-type cladding layer, each being a III-V group compound semiconductor, supported on a substrate of n-type GaAs, a p-type band discontinuity reduction layer of a III-V group compound semiconductor on the p-type cladding layer, and a p-type GaAs cap layer on the band discontinuity reduction layer. The p-type cladding layer, the p-type band discontinuity reduction layer, and the p-type cap layer are each doped with a p-type dopant which is lower in diffusivity than Zn. The p-type band discontinuity reduction layer has a concentration of a p-type dopant lower in diffusivity than Zn of 2.5.times.10.sup.18 cm.sup.-3 or higher to attain desired device characteristics, for example, high power output and efficiency.