To provide a paper sheet processing device arranging a reference bar code near a bar code reading position and which gives a bar code reader warning in occurring a change in reading rate of a bar code during power-on.

Firstly, at the power-on of the device, it makes a reading diagnosis on a reference bar code (reference BC) two thousands times continuously to calculate the reading rate. As the result of the reading diagnosis, if there is no abnormal reading, the device terminates an initial diagnosis. During the stoppage of the device, or if the device stops due to a diagnosis cause, in a business mode such as calculating processing after the completion of the initial diagnosis, the device makes a reading diagnosis on a reference BC to calculate the reading rate. If the reading rate has changed in comparison to the reading rate at the power-on, the device displays bar code reader warning (BCR warning) to an operator. The operator can clean or check the bar code reader on the basis of the warning display, so that the device can assure its reliability and improve its use efficiency.