A method of making a nitride semiconductor laser comprises forming a first InGaN film for an active layer on a gallium nitride based semiconductor region, and the first InGaN film has a first thickness. In the formation of the first InGaN film, a first gallium raw material, a first indium raw material, and a first nitrogen raw material are supplied to a reactor to deposit a first InGaN for forming the first InGaN film at a first temperature, and the first InGaN has a thickness thinner than the first thickness. Next, the first InGaN is heat-treated at a second temperature lower than the first temperature in the reactor, while supplying a second indium raw material and a second nitrogen raw material to the reactor. Then, after the heat treatment, a second InGaN is deposited at least once to form the first InGaN film.