An image forming apparatus includes a tray feeder to feed a printing medium placed on a tray of the image forming apparatus to an image former of the image forming apparatus, the tray moveable to be in a first position and a second position, a cassette feeder to feed a printing medium placed in a cassette of the image forming apparatus to the image former, a power train to transmit power generated from a driving motor, and a power switching unit to switch the power transmitted from the power train.