A movable side mounting portion transmits extension and contraction of a polymer actuator to an electric prosthetic hand. The polymer actuator deforms elastically in accordance with voltage application and returns to its original shape in accordance with stoppage of voltage application. A rear end of the polymer actuator is fixed and a front end of the polymer actuator is movable. When one of a pair of electrodes of the polymer actuator is electrically connected to the fixed side mounting portion, the fixed end is fastened by a bolt to the fixed side mounting portion. Also, when the other electrode is electrically connected to the movable side mounting portion, the movable end is fastened by a bolt to the movable side mounting portion.
