PURPOSE: To realize the response of displacement at a free terminal even in the number of oscillation of a band area higher than the number of first-order oscillation and to accurately perform focusing by preventing the free terminal of a supporting member possible to be rocked in which a quantity of displacement different from that of a displacement member can be obtained from being conformed to the node of the oscillation for the oscillation of the displacement member consisting of a piezoelectric or electrostrictive element provided in a cantilever shape.

CONSTITUTION: A cantilever 1 is provided with the displacement member 2 consisting of the piezoelectric or electrostrictive elements jointed by superposing mutually and the supporting member 3, and the supporting member 3 is formed integrally by performing the integral molding or joint of its base part 3a with the displacement member 2, and an inner edge in a range except for the base part 3a is separated from the outer peripheral edge of the displacement member 2 by providing a cavity, and the free terminal extends beyond that of the displacement member 2. Therefore, it is possible to prevent the free terminal of the supporting member 3 from being conformed to the node of the oscillation. In such a way, it is possible to obtain the response of the displacement at the free terminal in the supporting member by using the oscillation in the band area higher than the number of first-order resonance at the displacement member.