A caster unit includes a base member attached to a mobile body; a link mechanism rotatably supported by the base member to be capable of swinging up and down; an axle supported by the link mechanism; and a support mechanism provided between the axle and the base member, the support mechanism being configured to extends/contracts in a direction parallel to a tangent line of a trajectory of the axle that swings by the link mechanism to generate a damping force and a restoring force.