A quantum cascade laser includes a laser structure including laser waveguide structures and a first terrace region; first electrodes; pad electrodes; and wiring metal conductors. The laser structure includes first, second and third regions arranged in a direction of a first axis. The third region is disposed between the first and second regions. The first region has a first end facet disposed at a boundary between the first and third regions. The first end facet extends in a direction intersecting with the first axis. The second region has a second end facet disposed at a boundary between the second and third regions. The second region includes the laser structure. The pad electrodes are disposed on the first terrace region. The first electrodes are disposed on the laser waveguide structures. Each of the pad electrodes is connected to one of the first electrodes through one of the wiring metal conductors.