A photoconductive drum driving gear usable with an image forming apparatus includes a driving shaft, a driving gear to rotate with the driving shaft in connection with the driving shaft and meshed with a photoconductive drum gear of a process cartridge of the image forming apparatus, and a connection unit to connect the driving gear and the driving shaft so that the driving gear rotates with respect to the driving shaft by a predetermined angle when mounting the process cartridge to a main body of the image forming apparatus. The connection unit includes a plurality of connection projections formed at one of the driving shaft and the driving gear, a plurality of connection recesses formed at the other one of the driving shaft and the driving gear to correspond with the connection projections and having a greater width than the connection projections, and an elastic member interposed between the connection projections and the connection recesses to elastically bias the driving gear in a certain direction with respect to the driving shaft.