A base for a photosensitive drum composed of a resin composition attached to a high-speed image forming apparatus has a structure in which a gear is attached to one end of the base body through a flange part of 0.1 to 5 mm in thickness. The base is integrally molded by injection molding, and therefore the gear is not deformed when released from the mold. As a result, a photosensitive drum produced from the base has a good rotation precision and a good drive transmission and enables formation of high-quality image.