A method for fabricating a semiconductor laser includes: sequentially forming a cladding layer of a first conductivity type, an active layer, a cladding layer of a second conductivity type, and a contact layer of the second conductivity type on a semiconductor substrate; forming a promotion film which contacts the contact layer only in a window region proximate an end plane of the semiconductor laser and absorbs group-III atoms from the contact layer to promote generation of group-III vacancies; implanting ions into the contact layer in the window region to damage the contact layer in the window region; and after forming the promotion film and implanting the ions, heat treating so that the group-III vacancies are diffused and the active layer is disordered in the window region and forms a window structure.