To provide a coin processing device capable of paying exact changes and an automatic ticket vending machine on which the coin processing device is mounted.

The coin processing device is provided with an arm member 53 to be displaced according to external diameters of coins to be ejected from a hopper by considering that the external diameters of the coins are differentiated by every money type and a photosensor 58 to output pulses corresponding to a slit 70 of a slit board 57 provided on the arm part 53. Whether or not the coin to be emitted is a different money type is discriminated based on a fact that the pulses to be outputted from the photosensor 58 are different from those of the normal and different money types.