A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, wherein the main assembly includes a rotatable first main assembly drive transmission member and a rotatable second main assembly drive transmission member, said process cartridge comprising: an electrophotographic photosensitive drum; a drum unit containing said electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum with a developer; a developing unit containing said developing roller and movably connected with said drum unit, said developing unit being movable relative to said drum unit between a contact position in which said developing roller contacts said electrophotographic photosensitive drum and a spaced position in which said developing roller is spaced from said electrophotographic photosensitive drum; a drum coupling member, provided on one axial end of said electrophotographic photosensitive drum, for engaging with the first main assembly drive transmission member 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 along an axial direction of said electrophotographic photosensitive drum; and a shaft coupling member, provided on one axial end of said developing roller, capable of transmitting a second rotational driving force with a deviation permitted between an axis of the second main assembly drive transmission member and an axis of said developing roller with respect to a direction crossing the axis of said developing roller, wherein said shaft coupling member includes an engaging portion configured to engage with the second main assembly drive transmission member and to receive the second rotational driving force, when said process cartridge is mounted to the main assembly of the apparatus; said engaging portion being movable in the direction crossing the axis of said developing roller; characterized in that the drum unit comprises a holding portion (11c; 11f; 27f) capable of holding said engaging portion at such predetermined position relative to the process cartridge that when said process cartridge enters said main assembly of the apparatus with said developing unit positioned in the spaced position, the engaging portion is positioned engageably with the second main assembly drive transmission member by the holding portion (11c; 11f; 27f) while an axis (23c5) of said engaging portion is deviated from the axis of said developing roller with respect to the direction crossing the axis of said developing roller. an electrophotographic photosensitive drum; a drum unit containing said electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum with a developer; a developing unit containing said developing roller and movably connected with said drum unit, said developing unit being movable relative to said drum unit between a contact position in which said developing roller contacts said electrophotographic photosensitive drum and a spaced position in which said developing roller is spaced from said electrophotographic photosensitive drum; a drum coupling member, provided on one axial end of said electrophotographic photosensitive drum, for engaging with the first main assembly drive transmission member 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 along an axial direction of said electrophotographic photosensitive drum; and a shaft coupling member, provided on one axial end of said developing roller, capable of transmitting a second rotational driving force with a deviation permitted between an axis of the second main assembly drive transmission member and an axis of said developing roller with respect to a direction crossing the axis of said developing roller, wherein said shaft coupling member includes an engaging portion configured to engage with the second main assembly drive transmission member and to receive the second rotational driving force, when said process cartridge is mounted to the main assembly of the apparatus; said engaging portion being movable in the direction crossing the axis of said developing roller; characterized in that the drum unit comprises a holding portion (11c; 11f; 27f) capable of holding said engaging portion at such predetermined position relative to the process cartridge that when said process cartridge enters said main assembly of the apparatus with said developing unit positioned in the spaced position, the engaging portion is positioned engageably with the second main assembly drive transmission member by the holding portion (11c; 11f; 27f) while an axis (23c5) of said engaging portion is deviated from the axis of said developing roller with respect to the direction crossing the axis of said developing roller.