A semiconductor laser having a high electrostatic withstand voltage, resistant to a power supply surge, and having improved long-term reliability is obtained by reducing current leakage through a threading dislocation portion. The semiconductor laser includes a substrate having a high dislocation region having a dislocation density of 1×105 cm−2 or more, a crystalline semiconductor structure located on the substrate and having an active layer, an insulating film located on the semiconductor structure, a surface electrode located on the insulating film and electrically continuous with the semiconductor structure for injection of a current into the active layer, and a back electrode located on a rear surface of the substrate. The semiconductor laser has a laser resonator with a length L, and the area of the surface electrode is 120×L μm2 or less.