A punching processing unit punches holes in a paper bundle delivered from a preprocessing device. A bookbinding unit includes a cartridge for stocking a plurality of rings, and performs a ring binding by binding the paper bundle with the rings. A detecting unit detects an abnormality of a ring in the cartridge. A control unit exchanges a signal with the preprocessing unit each time when detection information obtained by the detecting unit changes. When any one of the rings is determined as abnormal and an execution of ring binding is set, the control unit inhibits the ring binding.