A sheet processing apparatus has: a plurality of conveying paths which convey sheets; and front and back aligning members which perform width alignment in the direction which crosses the sheet conveying direction of the sheets conveyed from the conveying paths. Standby positions when the front and back aligning members approach side edges of the sheets from the standby positions and perform the width alignment of the sheets at the width aligning position are made different every sheet on the basis of discharge position information of the sheets to the plurality of conveying paths.