A substrate with a nitride semiconductor layer is cleaved to form resonator end faces, on which a coating film is formed so as to make a nitride semiconductor laser bar. This is divided into nitride semiconductor laser elements. Prior to forming the coating film on the resonator end face, the resonator end face is exposed to a plasma atmosphere generated from the gas containing nitrogen gas. When a ratio of nitrogen to gallium in the surface of the resonator end face before the exposure is represented by “a”, an average value of ratios of nitrogen to gallium inside from the surface of the resonator end face before the exposure is represented by “b”, a ratio of nitrogen to gallium in the surface of the resonator end face after the exposure to the first plasma atmosphere is represented by “d”, and an average value of ratios of nitrogen to gallium inside from the surface of the resonator end face after the exposure is represented by “e”, the value “g” that is expressed by g=(b·d)/(a·e) is set to a value that satisfies g≧0.8.