ACTIVE CASTER

To provide an active caster adapted to suppress the decline in the driving performance. An active caster according to the present disclosure includes: a wheel; a first rotation transmission mechanism; and a second rotation transmission mechanism. A rotational force of a motor is transmitted to a rotation of the wheel about a pivot axis along a vertical axis via the first rotation transmission mechanism, the rotational force of the motor is transmitted to the rotation of the wheel about an axle via the first rotation transmission mechanism and the second rotation mechanism, and r/G>s holds true, where s>0 represents an offset of the axle from the pivot axis in a horizontal direction orthogonal to the axle, G represents a reduction ratio of the second rotation transmission mechanism, and r represents a radius of the wheel.