A quantum cascade laser includes a substrate having a conductivity type, substrate having a first region, a second region, and a third region; a semiconductor lamination provided on a principal surface of the substrate, the semiconductor lamination including a mesa stripe section provided on the second region, an upper cladding layer having the same conductivity type as the substrate, a first burying layer, and a second burying layer, the mesa stripe section including a core layer; and an electrode provided on the semiconductor lamination. The first and second burying layers are provided on the first and third regions and on both side faces of the mesa stripe section. The upper cladding layer is provided on the mesa stripe section, the first burying layer, and the second burying layer. The first and second burying layers include a first and second semi-insulating semiconductor regions comprised of a semi-insulating semiconductor material.