Gear device for vehicle seat

A gear device is provided which transmits a rotational force to a movable portion of a vehicle seat. The gear device of the present disclosure includes a rotation body, a second gear, a third gear, a fourth gear, and a thrust bearing portion. The thrust bearing portion is configured to make a sliding contact with an axial end surface of a shaft protruding from the second gear. The thrust bearing portion is configured to make the sliding contact with an area of the axial end surface on a first gear side of a border portion specified in advance.