To obtain high output and high reliability with less deterioration of an element by COD irrespective of film quality of a protection film, in a semiconductor laser element having the protection films on both end faces of a resonator in the manufacturing method of the semiconductor laser element.

The resonator end faces 1a and 1b are plasma-processed under a prescribed condition with low ion energy and high ion current density, for example. Thus, contaminant and a natural oxide layer are removed at the resonator end faces 1a and 1b which occur at the time of cleavage, and the resonator end faces 1a and 1b are reformed so that oxidation may be controlled.