Abstract: A tandem color image forming device comprises an image forming cartridge including a cartridge frame having a supporting part receiving a plurality of image forming units in parallel to modularize in a body, and a movable fixing part supporting at least one of a plurality of center shafts of photosensitive bodies disposed in the plurality of image forming units to be unmovable, but rotatable, and the other of the plurality of center shafts of the photosensitive bodies to be movable and rotatable when the plurality of image forming units are received in the cartridge frame, and a mounting frame formed at a main body to mount the image forming cartridge therein, and having a shaft receiving part formed at a position corresponding to both ends of the center shafts of the photosensitive bodies of the image forming units to receive both ends of the center shafts of the photosensitive bodies when the image forming cartridge is mounted in the mounting frame.