PURPOSE: To obtain an energy-confining type piezo-resonator that can be used in a kHz frequency band and in which a wider frequency band characteristic can be obtained by comprising a resonating part so as to resonate in a flexing vibration mode by vibration propagated via a vibration transmission part.

CONSTITUTION: A cylindrical supporting rod 4 is erected on the upper plane of a vibration test machine 3, and a steel iron bar 5 that can be vibrated in a flexing mode is fixed at the middle position of the supporting rod 4. The steel iron bar 5 is fixed in a state where the supporting rod 4 is inserted to a through hole provided in the center of the steel iron bar 5. The resonance frequency of the steel iron bar 5 in flexing at that time is assumed as around 1kHz. When the vibration test machine 3 is vibrated with frequency of 1kHz upward and downward as shown in arrowhead in figure, the amount of displacement of the upper terminal 4a of the supporting rod 4 is reduced to 1/10 by providing the steel iron bar 5 compared with the case where no steel iron bar 5 is provided, which generates sufficient attenuation at the part of the steel iron bar 5. In other words, propagated vibration can be cancelled by the steel iron bar 5 functioning as a resonator, and energy can be confined.