PURPOSE: To avoid positional shift of a piezoelectric element attended with mechanical contraction/expansion change of an elastic member by forming a notch to a part of the elastic member for holding the piezoelectric element placed between one piezoelectric element and other adjacent piezoelectric element.

CONSTITUTION: A part of an elastic member 11 placed between both the piezoelectric elements 9, 9, that is, the center of the elastic member 11 in lengthwise direction is formed with notches 23, 23 inward from the opposite side face. In case of the elastic member 11 provided with the notches 23, 23 in this way, a contraction/expansion change is caused in the lengthwise direction, it is absorbed by the notches 23, 23, since the member is made of an anisotropic conductive rubber sheet, the contraction/ expansion change is caused in the lengthwise direction on the characteristic of types of material depending on the environmental condition, the change is absorbed by notches 23, 23, the change does not give effect on the press contact face with the piezoelectric elements 9, 9. Thus, no position deviation is caused in each holding position for the piezoelectric elements and the elements are held at a prescribed position, that is, among pillar projections 6... and not in contact with each pillar projection 6, and the characteristic variation is suppressed.