To provide a reverse input preventing clutch that has a function for transmitting input torque from an input side to an output side and locking revere input torque from the output side to prevent it from backing up to the input side, and is compact, light and inexpensive.

The reverse input preventing clutch comprises, as principal elements, an input side member 1, an output side member 2, a rotationally restrained stationary side member 3, a locking means, an unlocking means and a torque transmitting means. The input side member 1, the output side member 2, the stationary side member 3 and a fixed side plate 4 are a pressed product of a metal plate such as a steel plate. Reverse input torque on the output side member 2 and the like is locked on the stationary side member 3 in both normal and reverse rotation directions by rollers 6 as the locking means. Input torque in both normal and reverse rotation directions from the input side member 1 is transmitted to the output side member 2 via holes 1d and projections 2d as the torque transmitting means.