To provide a torque transfer device Z having a nonreversible mechanism 4 which does not transfer rotation to an input shaft even when back drive acts on an output shaft, which reduces brake torque or enables a halt at the time of drive from the input shaft, thus which can realize fovorable torque efficiency of a system.

The torque transfer device is provided with a pair of a first plate A and a second plate B, a ball 11 on the input side, a fifth plate C and a shaft 41. A ball lamp 12 on the input side, which is for detecting prescribed torque, is formed on the pair of the first plate A and the second plate B. Then the ball 11 on the input side is housed in the ball lamp 12 on the input side, and the fifth plate C and the shaft 41 are for reducing an energizing force acting on a brake part 3 by the displacement of the first plate A in the axis direction.