There is provided a sheet processing apparatus with improved visibility of a sheet bundle discharged without post-processing thereto. The CPU circuit receives the conveyed sheet, drives and controls the sheet-returning paddle, the rack part, the rear end regulation part, the alignment plate and the like and forms sheet bundle comprising of a plural number of sheets as received. Further, the CPU circuit drives and controls the alignment plate when discharging the sheet bundle S from the processing tray, the sheet bundle S exceeding the number of sheets which can be post-processed by the stapler. Therefore, the sheet bundle S which includes sheets equal to the allowable number of sheets for post-processing of the sheet processing unit is discharged to the second discharge position which is different from the first discharge position.