A plating method and apparatus for a substrate fills a metal, e.g., copper, into a fine interconnection pattern formed in a semiconductor substrate. The apparatus has a substrate holding portion 36 horizontally holding and rotating a substrate with its surface to be plated facing upward. A seal material 90 contacts a peripheral edge portion of the surface, sealing the portion in a watertight manner. A cathode electrode 88 passes an electric current upon contact with the substrate. A cathode portion 38 rotates integrally with the substrate holding portion 36. An electrode arm portion 30 is above the cathode portion 38 and movable horizontally and vertically and has an anode 98 face-down. Plating liquid is poured into a space between the surface to be plated and the anode 98 brought close to the surface to be plated. Thus, plating treatment and treatments incidental thereto can be performed by a single unit.