A one-way clutch comprising: a first rotation member that has a cylindrical shape, is a rotation member that is rotatable about a rotational shaft in a first direction and a second direction counter to the first direction, and includes an outer circumferential portion having gear teeth to which a rotational driving force is inputted from outside, an interior space formed inward in a diameter direction of the outer circumferential portion, a first lateral surface portion that is a lateral surface at one end side of the rotation member in an axial direction of the rotational shaft, and a second lateral surface portion that is a lateral surface at the other end side of the rotation member in the axial direction and has an opening portion (71D1) providing an external opening for the interior space; a second rotation member that has a disk shape, is mounted on the second lateral surface portion of the first rotation member, is a rotation member rotatable in an integral manner with the rotational shaft, and includes a pivotal supporting portion inserted in the interior space to pivotally support the rotational shaft; characterised in that the one-way clutch further comprises; a support shaft that is disposed in a protruding manner from the first lateral surface portion of the first rotation member toward the interior space in the axial direction of the rotational shaft; and a transmission member that is supported by the support shaft, and is movable in a sliding manner in the axial direction between a first position at which a rotational driving force in the first direction inputted to the first rotation member is transmitted to the second rotation member, and a second position at which a rotational driving force in the second direction inputted to the first rotation member is restricted from being transmitted to the second rotation member. a first rotation member that has a cylindrical shape, is a rotation member that is rotatable about a rotational shaft in a first direction and a second direction counter to the first direction, and includes an outer circumferential portion having gear teeth to which a rotational driving force is inputted from outside, an interior space formed inward in a diameter direction of the outer circumferential portion, a first lateral surface portion that is a lateral surface at one end side of the rotation member in an axial direction of the rotational shaft, and a second lateral surface portion that is a lateral surface at the other end side of the rotation member in the axial direction and has an opening portion (71D1) providing an external opening for the interior space; a second rotation member that has a disk shape, is mounted on the second lateral surface portion of the first rotation member, is a rotation member rotatable in an integral manner with the rotational shaft, and includes a pivotal supporting portion inserted in the interior space to pivotally support the rotational shaft; characterised in that the one-way clutch further comprises; a support shaft that is disposed in a protruding manner from the first lateral surface portion of the first rotation member toward the interior space in the axial direction of the rotational shaft; and a transmission member that is supported by the support shaft, and is movable in a sliding manner in the axial direction between a first position at which a rotational driving force in the first direction inputted to the first rotation member is transmitted to the second rotation member, and a second position at which a rotational driving force in the second direction inputted to the first rotation member is restricted from being transmitted to the second rotation member.