PURPOSE: To eliminate various failures caused by the binding of a recording paper bundle of an excessive number of sheets by a method wherein when the number of recording paper stacked after image forming exceeds a maximum binding number in an after-treatment device provided with a stapling part, a stapling action is brought to a stop.

CONSTITUTION: An after-treatment device 1 disposed adjacently to an image forming device 100 and provided with a carry-in port E receiving recording paper after image forming consists of a sorting part I for sorting the carried recording paper and a stapling part II for binding the discharged recording paper in a stacked state and discharging the bundle. In this device, the number of paper supplied is counted by a through sensor disposed near a paper supply part 102 or the like. When the counted value reaches a maximum binding number of a staple S, the actuation of an automatic circulation manuscript supply device 200 and the paper supply part 102 is temporarily stopped. In addition, after the stop action, recording paper subjected to copying so far is treated so as to be discharged on a discharge tray through a staple tray 2 at a time.