To control generation of micro-crack and peeling through enhancement of wear-proof characteristic of contact area, by forming the surface of contact material with a layer including WC in a piezoelectric actuator for relatively shifting the contact material and a body to be driven.

A chip is pressed to the surface of a rotor with a spring by utilizing the rotor having a hard surface layer and the chip. A rotary torque sensor comprising a motor is placed in contact with the rotor, and a signal is given to the motor of a torque sensor to rotate at a constant speed. As the surface hard layer of the chip, WC is used and as the surface hard layer of the rotor, tufftride, aluminum and TiCN are used. As a result, the friction coefficient and wear-proof characteristic of the contact areas of contact member forming the drive transfer area and the part to be driven can be enhanced.