A laser diode with an improved kink level in the L-I characteristic and capable of obtaining a stable high output in a horizontal transverse mode is provided. The laser diode includes an active layer made of nitride III-V compound semiconductor containing at least gallium (Ga) in 3B-group elements and at least nitrogen (N) in 5B-group elements, an n-type compound semiconductor layer provided on one of faces of the active layer, and a p-type compound semiconductor layer provided on the other face of the active layer. A region closest to the active layer, in the n-type compound semiconductor layer is a high-concentration region whose impurity concentration is higher than that of the other n-type regions.