To provide a back-feed preventing mechanism, capable of preventing the movement of a coin moving in the direction opposite to the conveying direction even though it has a simple constitution.

This reverse-feed preventing mechanism is provided with a conveying belt 21 for loading and conveying a coin 2, a conveying roller 22 for driving the conveying belt 21, and a driven roller 12 driven by the conveying roller 22 via the conveying belt 21, the driven roller 12 holds the conveying belt 21 with the conveying roller 22, and stops the coin 2, moving from the direction which is reverse to the conveying direction of the conveying belt 21 by rotation.