An ultrasound operation apparatus comprising: an ultrasound transducer capable of generating ultrasound oscillation; a probe having a proximal end section operatively coupled to the ultrasound transducer and a distal end section and configured to generate ultrasound oscillation for treating a living tissue, the probe configured to transmit the ultrasound oscillation generated by the ultrasound transducer from the proximal end section to the distal end section; a resonant frequency tracking section configured to automatically adjust a frequency of a drive signal so as to track a resonant frequency of the ultrasound transducer and cause the distal end section to ultrasound-oscillate at the resonant frequency; characterized in that the ultrasound operation apparatus further comprises: a detecting section configured to detect a level of cavitation generated by the probe by detecting a level of a frequency component signal including an integral signal of a frequency different from the resonant frequency based on the drive signal adjusted by the resonant frequency tracking section; and a control section configured to perform control so as to vary an output of the drive signal in accordance with a detection result of the detecting section wherein the frequency component signal is an integral signal of at least one of a frequency band ranging from 5% to 95% of the resonant frequency or a frequency band ranging from 105% to 195% of the resonant frequency. an ultrasound transducer capable of generating ultrasound oscillation; a probe having a proximal end section operatively coupled to the ultrasound transducer and a distal end section and configured to generate ultrasound oscillation for treating a living tissue, the probe configured to transmit the ultrasound oscillation generated by the ultrasound transducer from the proximal end section to the distal end section; a resonant frequency tracking section configured to automatically adjust a frequency of a drive signal so as to track a resonant frequency of the ultrasound transducer and cause the distal end section to ultrasound-oscillate at the resonant frequency; characterized in that the ultrasound operation apparatus further comprises: a detecting section configured to detect a level of cavitation generated by the probe by detecting a level of a frequency component signal including an integral signal of a frequency different from the resonant frequency based on the drive signal adjusted by the resonant frequency tracking section; and a control section configured to perform control so as to vary an output of the drive signal in accordance with a detection result of the detecting section wherein the frequency component signal is an integral signal of at least one of a frequency band ranging from 5% to 95% of the resonant frequency or a frequency band ranging from 105% to 195% of the resonant frequency. a detecting section configured to detect a level of cavitation generated by the probe by detecting a level of a frequency component signal including an integral signal of a frequency different from the resonant frequency based on the drive signal adjusted by the resonant frequency tracking section; and a control section configured to perform control so as to vary an output of the drive signal in accordance with a detection result of the detecting section wherein the frequency component signal is an integral signal of at least one of a frequency band ranging from 5% to 95% of the resonant frequency or a frequency band ranging from 105% to 195% of the resonant frequency.