PURPOSE: To provide the control system of a paper money identifier, which can securely return non-appropriate paper money to a player by the alteration of the control system for identifying paper money so as to prevent the occurrence of injustice.

CONSTITUTION: In the paper money identifier of an inter-paper money base ball renting machine, in which the extraction preventing piece for paper money is provided in a transportation line and the passage recognition switch of paper money is interlocked to the extraction prevention piece, the excitation of a step motor 16, namely, an inverse operation is set to become an OFF state by setting the step motor pulse to be a negative state so as to return paper money to the player, by inverting the step motor 16, returning paper money to a paper money insertion port-side and setting the passage recognition switch of paper money interlocking with the extraction prevention piece 6 to become the OFF state when optical sensors 25 (25a-25c) and magnetic sensor 5 judge supplied paper money to be non-appropriate paper money, namely, forged money.