To provide a paper money processor for preventing a failure in returning paper money, by properly and quickly predicting a paper money jam in a conveyance path.

The rate Vr of reduction of rotation speed with respect to a reference time or the number of reference pulses of a conveyance motor 210 that drives a conveyance belt 40 for conveying paper money, is calculated at predetermined intervals when a paper money discrimination sensor 50 or the like detects paper money inserted from a paper money insertion slot 20 and conveyed in a conveyance path 10 by the conveyance belt 40. A control part 200 compares the calculated rotation speed reduction rate Vr with a threshold determined in association with a reference rotation time or a reference pulse number, and when the rotation speed reduction rate Vr exceeds the threshold, the conveyance motor 210 is reversed to quickly return the paper money to the paper money insertion slot 20.

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