PURPOSE: To provide a semiconductor laser element which has low threshold current, unified stable lateral oscillation mode and high light output by forming a current narrowing layer having a conductive type opposite to a substrate, forming a groove having a V-shaped section, and forming a double hetero junction layer on the groove, thereby reducing the lateral effective refractive index difference.

CONSTITUTION: A relationship of Eg2<Eg1<Eg3 exists among the forbidden band widths of a p type InGaAsP layer 13, an n type InP layer 12 and an InGaAsP active layer 11, where Eg1, Eg2, Eg3 respectively represent the forbidden band widths of the layers 13, 12, 11. The oscillation is produced by the current injection at the bent 17 of the layer 11 in a groove 16. Since the oscillation light exceeds the layer 12 to distribute to the layer 13, the effective refractive index difference becomes smaller than the case that only the n type InP layer exists as the waveguide layer. Since the layer 13 exists, the outside of the groove 16 becomes n-p-n-p-n junction, no current flows at the operating time, but the current flows concentrically only at the groove 16. Since the oblique surface of the groove 16 is (1-11) B surface or (2-1-1) surface, it becomes mirror surface, and the boundary with sP/InP is smooth, and no disorder occurs in the oscillation light mode image.