A quantum cascade laser includes a substrate having a principal surface; a laser body region disposed on the principal surface, the laser body region including a semiconductor laminate structure having an end facet, the laser body region having a waveguide structure extending along a waveguide axis; and a distributed Bragg reflection region disposed on the principal surface, the distributed Bragg reflection region including low and high refractive index portions that are alternately arranged in a direction of the waveguide axis. The end facet of the semiconductor laminate structure is optically coupled to the distributed Bragg reflection region. Each of the high refractive index portions includes a semiconductor wall including upper and lower portions that are arranged in a direction intersecting with the principal surface of the substrate. The principal surface is disposed between the upper and lower portions. The lower portion includes a part of the substrate.