The invention provides a process box in the use of an image forming device and an image forming device, characterized in that the process box in the use of the image forming device comprises: a drum shell that contains a sensitometric drum carrying developer images, wherein the sensitometric drum is in a form of cylinder and rotatably supported by the drum shell around its rotating shaft; and a developer shell that is detachably mounted on the drum shell; wherein any one of the drum shell and the developer shell has a plate rib which extends at a direction vertical to the rotating shaft of the sensitometric drum; the other one thereof has a positioning unit that is jointed with the rib and positions the drum shell and the developer shell at the direction of the rotating shaft of the sensitometric drum.