A color electrophotographic image forming apparatus for forming an image on a recording material, said apparatus comprising: (i) a mounting portion (100, 102, 103) configured to detachably mount a plurality of process cartridges (9a - 9d) each including an electrophotographic photosensitive drum (1a - 1d) and a developing roller (4a - 4d) for developing an electrostatic latent image formed on said electrophotographic photosensitive drum (1a - 1d), wherein said developing roller (4a - 4d) is movable between a contact state where said developing roller (4a - 4d) is contacted to said electrophotographic photosensitive drum (1a - 1d) and a spaced state where said developing roller (4a - 4d) is spaced from said electrophotographic photosensitive drum (1a - 1d), wherein said process cartridges (9a - 9d) are configured to develop the electrostatic latent images with colors different from each other; (ii) switching means (10a - 10d) configured to switch said developing rollers (4a - 4d) between the contact state and the spacing state when said process cartridges (9a - 9d) are set in said mounting portion (100, 102, 103); (iii) a feeding belt configured to feed the recording material along all of said electrophotographic photosensitive drums (1a - 1d) of said process cartridges (9a - 9d) set in the mounting portion (100, 102, 103); (iv) a driving force transmitting member configured to move the feeding belt into a first position for contacting to all of said electrophotographic photosensitive drums of said process cartridges and a second position wherein said feeding belt contacts only the electrophotographic photosensitive drum of a said process cartridge which develops the electrostatic latent image for image formation; and (v) control means configured to determine a kind of the recording material and, in a monochromatic mode operation, to switch in accordance with the determined kind of the recording material between a first mode in which said feeding belt is placed by said driving force transmitting member at said first position and a second mode in which said feeding belt is placed by said driving force transmitting member at said second position; wherein in the monochromatic mode, the image is formed on the said recording material through development of only one of said process cartridges (9a - 8d), and wherein in a process cartridge in which no development is performed in the monochromatic mode, said switching means (10a, 10b, 10d) is in the spaced state. (i) a mounting portion (100, 102, 103) configured to detachably mount a plurality of process cartridges (9a - 9d) each including an electrophotographic photosensitive drum (1a - 1d) and a developing roller (4a - 4d) for developing an electrostatic latent image formed on said electrophotographic photosensitive drum (1a - 1d), wherein said developing roller (4a - 4d) is movable between a contact state where said developing roller (4a - 4d) is contacted to said electrophotographic photosensitive drum (1a - 1d) and a spaced state where said developing roller (4a - 4d) is spaced from said electrophotographic photosensitive drum (1a - 1d), wherein said process cartridges (9a - 9d) are configured to develop the electrostatic latent images with colors different from each other; (ii) switching means (10a - 10d) configured to switch said developing rollers (4a - 4d) between the contact state and the spacing state when said process cartridges (9a - 9d) are set in said mounting portion (100, 102, 103); (iii) a feeding belt configured to feed the recording material along all of said electrophotographic photosensitive drums (1a - 1d) of said process cartridges (9a - 9d) set in the mounting portion (100, 102, 103); (iv) a driving force transmitting member configured to move the feeding belt into a first position for contacting to all of said electrophotographic photosensitive drums of said process cartridges and a second position wherein said feeding belt contacts only the electrophotographic photosensitive drum of a said process cartridge which develops the electrostatic latent image for image formation; and (v) control means configured to determine a kind of the recording material and, in a monochromatic mode operation, to switch in accordance with the determined kind of the recording material between a first mode in which said feeding belt is placed by said driving force transmitting member at said first position and a second mode in which said feeding belt is placed by said driving force transmitting member at said second position; wherein in the monochromatic mode, the image is formed on the said recording material through development of only one of said process cartridges (9a - 8d), and wherein in a process cartridge in which no development is performed in the monochromatic mode, said switching means (10a, 10b, 10d) is in the spaced state.