PURPOSE: To provide a simply constituted and inexpensive one-way clutch by applying the constitution where a transmission member rotates due to the unidirectional rotation of an input member and moves nearer an output member to keep a ratchet in coupled state for transmitting the rotation of the input member to the output member via the transmission member.

CONSTITUTION: Upon the rotation of a power input section 1 in the direction of an arrow R, the end of a projection 6 rotates, while being in contact with the slope 7c of a notch 7, thereby causing a power transmission section 2 to move left in the illustration or toward a power output section 3. As a result, a ratchet pawl 8 gears with a ratchet recess 9 and, therefore, a driving force is transmitted from the power input section 1 to the power output section 3. When the section 1 rotates in a direction opposite to the arrow R, the section 2 moves right in the illustration. Also, when the end of the projection 6 comes in contact with the slope 7c of the deep section of the notch 7, the ratchet pawl 8 becomes completely disengaged from the ratchet recess 9, and the rotation of the section 1 is not transmitted to the section 3, resulting in idling state.