A p-type GaAs current block layer is stacked on a (100)-oriented n-type GaAs substrate, and a stripe-shaped groove is formed in the p-type GaAs current block layer to extend in the direction. Side surfaces of the groove has the maximum inclination not larger than 60.degree.. The thickness of the p-type GaAs current block layer is 1.5 .mu.m or more. Stacked on the structured substrate having the current narrowed mechanism via an n-type ZnSe buffer layer are an n-type ZnMgSSe cladding layer, n-type ZnSSe waveguide layer, active layer, p-type ZnSSe waveguide layer, p-type ZnMgSSe cladding layer, and others, to establish an index-guided inner-striped semiconductor laser having SCH structure and CSPW structure.