Abstract: A paper feeder for feeding papers to an image forming apparatus and a paper tray elevation device therefore are disclosed. A first tray is movable up and down with a plurality of papers stacked thereon. A paper feed member feeds the papers from the first tray in a preselected direction of paper feed. A second tray is positioned beside the first tray in substantially the horizontal direction and movable up and down with a plurality of papers stacked thereon. A shifting device shifts the entire paper stack from the second tray to the first tray. A horizontal elevating mechanism elevates the first tray while maintaining it in substantially the horizontal position. An interlocking mechanism at least elevates, when papers of greater in size than the papers to be stacked on the first or second tray are stacked over the first and second trays in a single stack, the second tray in interlocked relation to the elevation of the first tray while maintaining the second tray in substantially the horizontal position.