A semiconductor laser including: a nitride III-V compound semiconductor substrate configured to have a first planar area, a second planar area, and a third planar area in a major surface, the first planar area being formed of a C-plane, the second planar area being continuous with the first planar area and being formed of a semipolar plane inclined to the first planar area, the third planar area being continuous with the second planar area and being formed of a C-plane parallel to the first planar area; a first cladding layer configured to be composed of a nitride III-V compound semiconductor on the major surface of the nitride III-V compound semiconductor substrate; an active layer configured to be composed of a nitride III-V compound semiconductor that exists on the first cladding layer and contains In; and a second cladding layer configured to be composed of a nitride III-V compound semiconductor on the active layer.