A print-medium storing unit, a print-medium storing apparatus including the same, and an image forming apparatus including the same which may be provided in a power transmission mechanism, print-medium storing apparatus which may be installed on a discharge path of a print-medium in an image forming apparatus, includes a plurality of storing units which is arranged with multi-layers, and a controller which controls to drive a feeding unit of another storing unit arranged between the storing unit through which the print-medium is to be discharged and the image forming apparatus, by a driving source of the storing unit through which the print-medium is to be discharged.