A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus includes an electrophotographic photosensitive drum, a process device actable on the drum, a drum frame, first and second drum frame openings at a different longitudinal ends of the drum frame, first and second end regulating portions at different longitudinal ends of the drum frame, a drum shaft with a through hole, a drum end flange with an end flange opening for receiving the drum shaft, first and second openings provided opposite from each other at a periphery of the end flange opening, and a connecting member penetrating the first opening and the through hole and engaged with the second opening to connect the photosensitive drum with the drum shaft. The regulating portions regulate the position of the drum in its longitudinal direction and the connecting member connects the drum shaft with the drum.