A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising: (i) a drum unit; (ii) a developing unit; and (iii) an urging member (54, 49), wherein said drum unit includes: (i-i) an electrophotographic photosensitive drum, (i-ii) a holding portion, and (i-iii) a drum coupling member, provided on one axial end of said electrophotographic photosensitive drum, for engaging with a first main assembly drive transmission member provided in the main assembly of the apparatus and transmitting a first rotational driving force to the electrophotographic photosensitive drum, when said process cartridge is mounted to the main assembly of the apparatus, wherein said developing unit includes: (ii-i) a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum with a developer, and (ii-ii) a shaft coupling member for transmitting a second rotational driving force from a second main assembly driving force transmission member provided in the main assembly with a deviation permitted between an axis of the second main assembly drive transmission member and an axis of said developing roller, said shaft coupling member including (ii-iii) an engaging portion for engaging with the second main assembly drive transmission member and receiving the second rotational driving force, and wherein said engaging portion is movable in a direction crossing with the axis of said developing roller; characterized in that said shaft coupling member is provided on one axial end of said developing roller; said urging member urges said engaging portion in the crossing direction toward said holding portion; when said process cartridge enters the main assembly of the apparatus, said engaging portion is positioned to said holding portion; when said process cartridge is moved by movement of a movable member provided in the main assembly of the apparatus from a first position to a second position, said engaging portion is positioned to a main assembly locking member provided in the main assembly of the apparatus and said process cartridge is positioned to a main assembly positioning portion provided in the main assembly of the apparatus; and a distance between an axis of said engaging portion and an axis of said developing roller is smaller when said process cartridge is positioned to the main assembly positioning portion than when said engaging portion is positioned by said holding portion. (i) a drum unit; (ii) a developing unit; and (iii) an urging member (54, 49), (i-i) an electrophotographic photosensitive drum, (i-ii) a holding portion, and (i-iii) a drum coupling member, provided on one axial end of said electrophotographic photosensitive drum, for engaging with a first main assembly drive transmission member provided in the main assembly of the apparatus and transmitting a first rotational driving force to the electrophotographic photosensitive drum, when said process cartridge is mounted to the main assembly of the apparatus, (ii-i) a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum with a developer, and (ii-ii) a shaft coupling member for transmitting a second rotational driving force from a second main assembly driving force transmission member provided in the main assembly with a deviation permitted between an axis of the second main assembly drive transmission member and an axis of said developing roller, said shaft coupling member including (ii-iii) an engaging portion for engaging with the second main assembly drive transmission member and receiving the second rotational driving force, and