PROBLEM TO BE SOLVED: To provide a reverse input cutoff clutch which can reduce noise and vibration generated from inside in either a high-temperature environment or a room-temperature environment. SOLUTION: The reverse input cutoff clutch 3 is provided with a rotatable input member 16, a rotatable output member 17, a stationary member 18 restricted in its rotation, a torque transmitting means 19 for transmitting input torque acting on the input member 16 to the output member 17, and a locking means 20 for cutting off the transmission of reverse input torque acting on the output member 17 to the input member 16. The locking means 20 locks the output member 17 and the stationary member 18 by an engaging element 15 arranged therebetween so as to cut off the transmission of the reverse input torque acting on the output member 17 to the input member 16. Grease having the penetration of 265 to 295 and mixed with organic molybdenum as an extreme-pressure additive, is interposed between the stationary member 18 and the output member 17 which are engaged or released by the engaging element 15. COPYRIGHT: (C)2007,JPO&INPIT