An electrophotographic amorphous silicon photosensitive member is used for an electrophotographic apparatus that forms images by the electrophotographic method, and an image forming apparatus uses this photosensitive member, which includes a drum-shaped cylindrical conductive substrate, and a photosensitive layer that contains amorphous silicon, thus structuring an electrophotographic photosensitive drum. Then, the outer diameter of this photosensitive drum is configured to be gradually smaller from the vicinity of the central portion thereof in the generatrix direction to both ends in the longitudinal direction, hence making it possible to enhance the cleaning effect on residual toner.