A color image forming device has an image forming cartridge including a cartridge frame that receives a plurality of image forming units. A movable fixing part supports at least one of the shafts of a plurality of photosensitive bodies disposed in the image forming units so that the shaft is rotatably fixed. The shafts of the other photosensitive bodies are movable and rotatable when the plurality of image forming units are received in the cartridge frame. A mounting frame receives the image forming cartridge, and has a shaft receiving part formed at a position corresponding to the ends of the shafts of the photosensitive bodies. The color image forming device accurately fixes the position of the shafts of the photosensitive bodies when the image forming cartridge is assembled in the mounting frame, thereby producing a high quality image reliably.