A semiconductor laser is a distributed feedback semiconductor laser in which the lasing wavelength can be changed, and includes a semiconductor substrate and a semiconductor layer portion provided on the substrate and including first and second active layers and an intermediate layer that optically couples the first active layer and the second active layer. The first active layer, the intermediate layer, and the second active layer are arranged in that order in a predetermined axis direction. The semiconductor laser further includes a diffraction grating that is optically coupled with the first and second active layers of the semiconductor layer portion, a first electrode and a second electrode for injecting carriers into the first active layer and the second active layer, respectively, and a third electrode for supplying the intermediate layer with a current. The grating extends in the predetermined axis direction and has a period that is uniform in the predetermined axis direction.