A paper sheet or bill processing apparatus capable of reliably detecting a paper sheet or bill present in a traveling route. The paper sheet or bill processing apparatus includes: a motor for a paper sheet or bill conveyance mechanism which can be driven to convey a paper sheet or bill along a traveling route; a discharge sensor which detects whether or not the paper sheet or bill is present in the traveling route; and control means which carries out a redetection process to detect whether or not the paper sheet or bill is present in the traveling route again by the discharge sensor after the motor is driven if the paper sheet or bill is not detected by the discharge detection sensor in a detection process in a condition that driving of the conveyance mechanism is stopped.