A tire manufacturing device capable of precisely mounting a circular tread on a base tire with the center of the base tire in the widthwise direction thereof and the center of the annular tread in the widthwise direction thereof made to coincide with each other. A tire manufacturing device is provided with a drum to which a base tire is affixed, holding means which hold the inner peripheral side of an annular tread, and movement means which move the holding means in the direction of the rotation axis of the drum in such a manner that the holding means approach or separate from the drum. The holding means are provided with conveyance means for causing the annular tread, which is held by the holding means, to approach or separate from the base tire. The conveyance means mount the annular tread to the outer peripheral surface of the base tire by conveying the annular tread in the approaching direction at the same speed as the holding means moves in the separating direction.