An image forming apparatus (1) includes a frame (61) supporting an attached object (23) inserted into an apparatus body (2) and an attachment device (62) fixing the attached object (23) supported by the frame (61). The frame (61) includes a leading end plate (61b) facing to a leading end in an inserting direction of the attached object (23). The attached object (23) includes a fixing pin (65) supported by the leading end plate (61b) in advanceable/retreatable state along the inserting direction and formed connectable to the attached object (23), a biasing member (66) biasing the fixing pin (65) toward the inserting direction and a locking member (67) restricting dropout of the fixing pin (65). The attachment device (62) holds the attached object (23) being connected to the fixing pin (65) and receiving the biasing force of the biasing member (67) at a position gravitated to the leading end plate (61b).