A process cartridge includes a photosensitive drum, a gear attachable to an end of the photosensitive drum in a longitudinal direction of the photosensitive drum, a shaft member capable of passing through an inside of the photosensitive drum and the gear so as to extend in the longitudinal direction of the photosensitive drum, and a frame having a pair of shaft supporting portions which supports both end portions of the shaft member at positions outside the photosensitive drum. One of the pair of shaft supporting portions functions as a gear-side supporting portion which is provided on a side where the gear is disposed. The gear includes a first insertion hole, into which the shaft member is inserted, and a projecting portion, which protrudes outward from a side, which is opposite to a side facing the end of the photosensitive drum, of the gear.