Provided is a sheet storing apparatus including a processing tray and a stack tray arranged respectively at the downstream side of a path sheet discharging port of a sheet discharging path and at the downstream side of the processing tray as forming a step respectively, and a reversing roller arranged at a tray sheet discharging port as being capable of rotating forwardly and reversely to convey a sheet conveyed from the path sheet discharging port selectively to the processing tray and the stack tray, so that a sheet to be conveyed to the processing tray from the path sheet discharging port is conveyed in a state of having corrugations formed thereon and a sheet to be conveyed to the stack tray from the sheet discharging port is stored at the stack tray in a flat shape as having the corrugations corrected after passing through the reversing roller.