A sheet feeder includes a sheet feed tray on which a first sheet bundle is stacked at a first position where sheet feeding to a conveyance path can be performed, and a conveyance tray on which a second sheet bundle is stacked at a second position adjacent to the sheet feed tray, and which conveys the second sheet bundle to the sheet feed tray and stacks the second sheet bundle on the sheet feed tray after the first sheet bundle is fed, presses the stacked second sheet bundle to a side plate provided in a direction perpendicular to a conveyance direction of the conveyance tray, and aligns an end of the second sheet bundle.