Patent ID: 7892364

Claim:
A method for surface-modifying an engine valve while holding said engine valve formed of an iron group series alloy on a surface-modifying jig, said surface-modifying jig including a surface contact area, a head part of said engine valve being brought into contact with said surface contact area, and said contact being a surface contact, wherein said surface-modifying jig comprises an inclined portion, which is inclined in accordance with the shape of said head part of said engine valve, and wherein said inclined portion is brought into surface contact with said head part, said method comprising the steps of: bringing said head part of said engine valve into contact with said surface contact area of said surface-modifying jig; and placing said surface-modifying jig inside a treatment furnace, and causing a discharge between a cathode and an anode in the presence of a flowing gas, thereby generating a plasma employing said gas as a source, wherein said surface-modifying jig or said engine valve serves as said cathode.