A semiconductor laser adaptable for a 3-beam method, including a semiconductor laser chip bonded on a primary plane of a flat submount, the semiconductor laser chip having a thickness of 30 to 80 .mu.m is provided. Also provided is a method for manufacturing a semiconductor laser including the steps of: sequentially stacking layers of compound semiconductor materials on a semiconductor substrate to form a semiconductor laser wafer; mechanically abrading the semiconductor substrate to make it thin; subjecting the mechanically abraded face of the semiconductor substrate to a chemical treatment; forming an electrode film on both sides of the semiconductor laser wafer thus treated; and cutting the semiconductor laser wafer into chips and bonding each of the chips on a submount.