A color electrophotographic image forming apparatus, wherein a plurality of cartridges is detachably mountable to a main assembly of the apparatus, includes a cartridge supporting member movable between an inside position which is inside the main assembly and an outside position which is outside the main assembly, supporting the cartridges, wherein the cartridges are mounted to and dismounted from the cartridge supporting member placed in the outside position, and wherein the cartridge supporting member is movable between the inside position and the outside position intersecting a feeding path of a recording material.