A control command communicated between a print control section and a finisher control section are relayed by an inserter control section. The print control section and the finisher control section generate the control command without taking into account processing at an inserter, and the inserter control section judges the content of the control command upon receiving the control command sent from the print control section or the finisher control section, and converts the control command or adjusts output timing of the control command if the control command needs to take into account the processing at the inserter.