A process cartridge, which uses a removable cartridge and also a one-property contact system, used with an image forming apparatus, includes a drum cartridge in which a photoconductive drum is disposed in an exposed manner, a toner cartridge in which a developing roller rotating in contact with the photoconductive drum is mounted in an exposed manner, and supporting members supporting and guiding the toner cartridge so that the developing roller moves linearly with respect to the photoconductive drum. The supporting members are made stationary in predetermined positions of the main body, and a developing nip between the photoconductive drum and the developing roller is controlled as the toner cartridge is moved linearly with respect to the supporting member within a predetermined distance range.