Provided is a sheet supply device capable of increasing the number of sheets to be loaded on a sheet supply tray without increasing a depth of the sheet supply tray. A sheet supply device provided with a sheet supply tray 10 on which a sheet is placed, a delivery roller 13 that contacts a topmost surface of a sheet bundle on the sheet supply tray 10 to deliver the sheet, and separation means 14 and 15 that feed the sheet delivered by the delivery roller 13 one by one in a separated manner includes an elevating tray 41 configured to be freely elevated/lowered so as to support a leading end side of the sheet bundle placed on the sheet supply tray and to move the topmost surface of the sheet bundle to a delivery position, a first drive section that elevates/lowers the elevating tray 41, a second drive section that elevates/lowers the delivery roller 13, and a controller that controls drive of the first and second drive sections, wherein the controller controls the first and second drive sections so as to elevate the elevating tray 41 until the topmost surface of the sheet bundle reaches the delivery position and thereafter lower the delivery roller 13 to a position where it contacts the topmost surface of the sheet bundle.