<p>An ultrasonic vibrator is an ultrasonic vibrator (10) of a shaft-integrated Langevin vibrator in which a shaft (12) around which piezoelectric elements (14) are coaxially stacked and a vibrator body (11) are integrally formed comprises a compression mechanism including a screw portion (13) at the end of the spindle and a pressurizing nut (17) having the substantially same thermal expansion coefficient as the shaft (12) and screwed onto the screw portion (13) to compress the piezoelectric elements (14) with the vibrator body (11), and a back element (16) stacked and compressed coaxially with the piezoelectric elements (14) around the shaft and having a thermal expansion coefficient and a thickness sufficient to accommodate the difference in axial thermal expansion between the shaft (12) and the piezoelectric elements (14). The change of pressurization force of the piezoelectric elements due to temperature change can be thus effectively reduced by a stable structure.</p>
