A method for producing a quantum cascade laser includes the steps of growing a stacked semiconductor layer including a core layer; forming an insulating mask on the stacked semiconductor layer; forming a mesa structure including the core layer by etching the stacked semiconductor layer through the insulating mask; growing a buried layer on a side surface of the mesa structure using the insulating mask by supplying a halogen-based substance and a gas containing a raw material, the buried layer having a thickness larger than a height of the mesa structure; producing a substrate product including the mesa structure and a buried region by processing of the buried layer using a chemical-mechanical polishing method; and after removal of the insulating mask, producing a distributed reflection structure by etching the mesa structure and the buried region of the substrate product using a mask.