Abstract: Disclosed is a process for the surface treatment of a conductive material which comprises the steps of disposing a DC electrode having a base material of the conductive material thereon and an RF electrode in a reaction vessel so that the electrodes are parallel to each other; forming a reduced pressure space of a predetermined gas in the vessel; and applying simultaneously a direct current voltage to the DC electrode and a radio-frequency power to the RF electrode so that a surface of the base material is subjected to bombardment treatment under DC discharge and RF discharge. Since the surface treatment of the present invention is effected while causing DC discharge and RF discharge simultaneously, film formation can be made on the thus surface-treated base material with a good adhesion. Further, an abnormal surface layer formed by electric discharge machining can be readily removed without leaving its corner portion and residual tensile stress introduced by electric discharge machining can also be relieved.