Abstract: To treat a corner of an etched metal machined article by a method other than polishing. A method includes: forming a protective layer 200 on each of a front surface 120 and a back surface 140 of a metal plate 100 while a side surface 160 of the metal plate 100 is exposed; cutting out a precursor 300 of a component to be manufactured from the metal plate 100 on which the protective layer 200 is formed; etching the precursor 300 without removing the protective layer 200; chamfering a corner between the front surface 120 and the side surface 160 and a corner between the back surface 140 and the side surface 160 of the etched precursor 300 by an electrical or chemical treatment; and removing the protective layer 200 from the chamfered precursor 300.