In order to correct a corrugation caused when a sheet widthwise edge portion elongates more than the vicinity of the center in a sheet feeding direction, a sheet processing apparatus includes: a fixing portion that fixes a toner image onto a sheet by heating, a plurality of pairs of rollers provided along a sheet feeding direction with an interval in the downstream of the fixing portion in the feeding direction to nip and convey a sheet; and a tensioning device that applies a tensile strength of the sheet feeding direction to a sheet in a center area of a width direction perpendicular to the sheet feeding direction.