A charging apparatus is provided in which electrodes can be protected from corrosion induced by water content in the air, ozone, nitrogen oxide and the like and thereby lack of uniformity in charged potential on photoreceptor surface can be prevented, and in which a charged potential on photoreceptor surface can be kept in an adequate range for a longer period of time. As an electrode disposed in the charging apparatus for charging photoreceptor surface, an electrode formed with a protective layer made of nickel and phosphorus for surface protection is used. In the protective layer, phosphorus concentration and thickness proportion are each set to fall within a specified range.