An electrophotographic printer capable of easily attaching and detaching a retaining means to retain the inside of a photoconductive drum to and from the photoconductive drum. A flange located on the extraction side of a photoconductive drum is provided with: a retaining means to support the photoconductive drum from the side of the inner circumferential face of the photoconductive drum. And an advance and retreat mechanism to advance and retreat the retaining means to and from the inner face of the photoconductive drum. The retaining means can be easily dismantled from the photoconductive drum by operating the advance and retreat mechanism, and thereafter extracting the flange from the photoconductive drum.