A reverse input blocking clutch comprises, as main elements, an input member, an output member, a stationary member for constraining the revolutions, locking means, lock release means and torque transmission means. By forming the input member, the output member, the stationary member and a fixed side plate from metal plates such as press worked steel plates, a compact, lightweight and low cost reverse input blocking clutch is provided. Reverse input torque from the output member is locked in both the forward and reverse rotational directions relative to the stationary member, by rollers which function as the locking means. Input torque from the input member in both the forward and reverse rotational directions is transmitted to the output member via apertures 1d and protrusions which function as the torque transmission means.