To transmit the rotating force in only one of normal and reverse directions by interposing an interlock member formed of plural divided parts between a drive rotary member and a driven rotary member, and widening the space between the divided parts while pushing them with a pushing member by making both the rotary members into power transmittable state.

When a driven rotary member 3 is rotated in one direction in a figure, a roller 8 as a wedge member is not moved even if the driven rotary member 3 is rotated, and the rotating force is not transmitted to a drive rotary member 2. In this condition, when the drive rotary member 2 is rotated, a roller 7 as a pushing member pushes each inclined surfaces 4a of each part 4A, 4B of an interlock member 4 to enlarge the diameter of the interlock member 4. As a result, the drive rotary member 2, the roller 7 and the interlock member 4 are made to pressure-contact with each other. The roller 8 bites into a bottom surface 4b of a recessed part of the interlock member 4 and the inner peripheral surface of the driven rotary member 3 so as to connect the interlock member 4 to the driven rotary member 3, and the rotating force is transmitted to the drive rotary member 2.