To simply and easily form a desired marking at a low cost while exposing a part of a metal surface or a paint by irradiating a painted face applied to a part to be treated made of metal with a laser beam in a scanning method, etc., and forming the engraving of a prescribed pattern.

Painting is applied to a metal part W to be treated of a formed part by aluminum die cast, by irradiating a paint 15 with a laser beam, the engraving of a prescribed pattern is formed by a scanning method, a mask method, a mask scanning method, etc. By this method, the paint 15 is removed over its whole thickness with a laser beam to expose the metal surface of a prescribed pattern, a desired marking 5 having the contrast between a painted face and a metal surface is formed. Further, plural layer paintings having different colors are applied to a part surface to be treated, an engraving depth of a paint is adjusted with a laser beam, thus, the marking emitting many colors can be formed.