In a conveying belt that is entrained about a pair of bundle discharge rollers along a stacking wall, on which an end part of a sheet stacked on a stack tray abuts, between the stack tray and an intermediate processing tray, a position of an outer peripheral surface is displaced such that a projection amount of the conveying belt from the stacking wall is large when the pair of discharge rollers discharges the sheet to the stacking portion, and such that the projection amount is small when the pair of discharge rollers moves the sheet toward a stopper of the intermediate stacking portion.