SPEED REDUCER

A speed reducer includes an input shaft member including a sun rotor arranged to rotate about a central axis; one or more planetary rolling elements each of which is supported to be capable of rotating around the sun rotor; a tubular eccentric shaft including an outer circumferential surface eccentric with respect to the central axis, and arranged to rotate about the central axis along with the rotation of the one or more planetary rolling elements; an eccentric oscillating gear including a plurality of external teeth in an outer circumferential surface thereof, and supported by the eccentric shaft through a first bearing; a housing including internal teeth arranged to mesh with the external teeth of the eccentric oscillating gear in an inner circumferential surface thereof; an output flange arranged to rotate about the central axis together with the eccentric oscillating gear, and including an eccentric oscillating carrier pin arranged to pass through the eccentric oscillating gear in an axial direction; and one or more second bearings arranged radially between an inner circumferential surface of the eccentric shaft and the input shaft member.