A method for manufacturing a laser diode includes: providing a semiconductor structure in which semiconductor layers are laminated; forming a waveguide ridge in the layers; forming an SiO2 film over the entire surface; forming a second resist pattern covering the SiO2 film in channels adjacent the waveguide ridge such that top surfaces of the second resist pattern in the channels are higher than the top surface of a p-GaN layer in the waveguide ridge and lower than the top surface of the SiO2 film on the top of the waveguide ridge, the second resist pattern exposing the top surface of the SiO2 film on the top of the waveguide ridge; removing the SiO2 film, using the second resist pattern as a mask, to expose the top surface of the p-GaN layer in the waveguide ridge; and forming an electrode layer on the top surface of the p-GaN layer.