To provide a paper sheet processor equipped with a binding device capable of properly setting the feed of a strip for binding paper sheets depending on the quality of the paper sheets to be processed.

The passage of the paper sheets P is detected in the inlet of an accumulation device 30, and the number of the accumulated paper sheets is counted when the paper sheets P are detected in the detection of the passage. Concurrently, a sum value Cfs of defective sheet levels is also computed, and these operations are repeated until the number of the accumulated paper sheets reaches 100. A mean value Cfav of the defective sheet levels is computed by dividing the computed sum value Cfs of the defective sheet levels by 100 as the number of the defective paper sheets. A pulse number corresponding to the amount of the pay-out of the strip corresponding to the computed mean value Cfav of the defective sheet levels is selected from a pulse table and set in a strip feeding pulse motor, so that the strip equivalent to the pulse number can be fed. After the completion of this strip feeding operation, a cutter solenoid is driven, and the band sending end of the strip is cut by a cutter. The strip is wound around the hundred paper sheets and heat-bonded by a heater.