To provide a paper sheets processing device capable of printing a serial binding strap number only when the actually counted serial binding strap number is matched with the incremented serial binding strap number.

An identification unit 12 notifies a printing unit 40 of the initial value of the serial binding strap number when the counting is started, and notifies the printing unit 40 of the printing start command and the serial binding strap number every time when the predetermined number of sheets are counted. The printing unit 40 increases the internally maintained serial binding strap number based on the notification of the printing start command and the serial binding strap number from the identification unit 12, and prints the serial binding strap number based on the matching of this serial binding strap number with the serial binding strap number notified from the identification unit 12.