A quantum cascade laser includes a substrate having first and second substrate regions arranged along a first axis; a laser structure body including a laser body region having laser waveguide structures extending along the first axis, the laser structure body including first and second regions respectively including the first and second substrate regions, the laser body region having an end facet located at a boundary between the first and second regions, the second region including a terrace extending along the first axis from a bottom edge of the end facet; a plurality of first electrodes disposed on the laser waveguide structures; a plurality of pad electrodes disposed on the terrace; and a plurality of wiring metal bodies each of which includes a first portion on the terrace and a second portion on the end facet. The pad electrodes are connected with the first electrodes through the wiring metal bodies, respectively.