This invention provides a circular body, which is used for an image forming apparatus employing an electrophotographic system, the circular body containing: at least an inner layer containing resin and an outer layer that is laminated on an outer circumferential surface side of the inner layer and contains resin; and, as a conductive agent, polyaniline in the outer layer and carbon black in the inner layer; and satisfying the following relational expressions (1) and (2): 13.0≦C1≦15.0  (1) 21.5≦C2≦25.0  (2), wherein C1 represents the content (parts by weight) of the polyaniline with respect to 100 parts by weight of the resin forming the outer layer, and C2 represents the content (parts by weight) of the carbon black with respect to 100 parts by weight of the resin forming the inner layer, as well as a circular body unit using the circular body and an image forming apparatus using the circular body.