A quantum cascade laser includes a laser structure including first and second end faces, the laser structure including a semiconductor laminate region and a first embedding semiconductor region. The laser structure includes first and second regions arranged in a direction of a first axis extending from the first to second end faces. Each of the first and second regions includes the semiconductor laminate region. The semiconductor laminate region of the first region has a first recess. The semiconductor laminate region of the second region has a semiconductor mesa. The first recess and the semiconductor mesa extend in the direction of the first axis, and are aligned with each other. The semiconductor mesa has an end face extending in a direction of a second axis intersecting the first axis. The first embedding semiconductor region is disposed in the first recess so as to embed the end face of the semiconductor mesa.