To solve a problem that a thin line electrode is easily crushed by clamping force generated by a laminated piezo element, since a fixing clamper and a driving clamper are made of a material harder than the thin line electrode for wear resistance.

The first and second driving clamper 9, 17 are composed of first and second superhard metal 12, 19 directly attached to the thin line electrode, and first and second Bakelites 13, 20 cemented with lower surfaces of the first and second superhard metal 12, 19. Therefore, clamping force generated when first and second piezo actuators 2, 3 clamp the thin line electrode 1 is partially absorbed by the first and second Bakelites 13, 20. Consequently, the clamping force added on the thin line electrode 1 becomes weak, and the possibility that the thin line electrode is crushed by the clamping force becomes small. Impact at clamping is also relieved, so that the possibility that the thin line electrode 1 is crushed becomes small.