PURPOSE: To provide a treating method by which the adhesive strength of a hard carbon film to the substrate has considerably been improved at a low temp. and obtain hard carbon film coated parts by adopting the method.

CONSTITUTION: The surface of a metallic substrate 11 is irradiated with excimer laser beams in an atmosphere of a silicon-contg. gas to form a silicon diffused layer 12 in the surface layer of the substrate 11 and a silicon deposited layer 13 on the surface layer. A hard carbon film 14 is then formed by vapor phase synthesis in an atmosphere of gaseous hydrocarbon. The objective hard carbon film is formed only on the part of the substrate requiring the film with satisfactory adhesion without exerting any thermal influence on the substrate itself.