Object is that an output sound pressure at transmission or an output voltage at reception of a predetermined higher resonance component becomes higher than those of the primary resonance component. The piezoelectric material layer 24 has an electrode on the surface of the piezoelectric material of between the layer and both ends, and outputs and inputs an electrical signal with this electrode. The piezoelectric material 24 has a remanent polarization in a thickness direction, the relationship of the (4P+1)th layer piezoelectric material from fixed end side is used as the basic relationship, piezoelectric materials are periodically arranged so that piezoelectric materials of (4p+2)th and (4p+3)th layer each has an opposite relationship, and (4p+4)th layer has the same relationship as the basic relationship. On the fixed-end side of the piezoelectric material layer 24, provided is the de-matching layer 23 with larger acoustic impedance than the piezoelectric material layer 24 for reflecting vibration propagated from the piezoelectric material layer 24 to the fixed-end side.
