Disclosed herein is a semiconductor laser including: a first clad layer of a first conduction type; an active layer over said first clad layer; a saturable absorbing layer over said active layer; and a second clad layer of a second conduction type over said saturable absorbing layer; at least said second clad layer being provided with a pair of grooves parallel to each other with a predetermined spacing therebetween so as to form a ridge stripe therebetween. In the semiconductor laser, the distance from bottom surfaces of said grooves to an upper surface of said active layer is not less than 105 nm, and the distance from said bottom surfaces of said grooves to an upper surface of said saturable absorbing layer is not more than 100 nm.