An apparatus (1; 1A) configured to detachably attach to a handpiece (40; 40X) equipped with an ultrasound transducer for generating ultrasound vibrations, and a probe provided with a proximal end portion coupled to the ultrasound transducer and a distal end portion to which the ultrasound vibrations are transmitted from the proximal end portion, wherein a class information storage portion is provided to the handpiece (40; 40X) and stores identification information that indicates a class of the handpiece (40; 40X), the apparatus comprising: a class information setting portion which, when connected to the handpiece (40; 40X), causes an electric signal to be transmitted from the class information storage portion to set the identification information; a drive portion which is connected to the ultrasound transducer and supplies the ultrasound transducer with a drive signal for generating the ultrasound vibrations; a detection portion configured to detect a signal level where only frequency components obtained by removing a resonance frequency of the drive signal are acquired, the signal level being a level of a cavitation level signal, the signal level corresponding to a state that the distal end portion is vibrated with ultrasound by a drive signal that causes vibration amplitude for calibration for causing the distal end portion of the probe to generate cavitation in a calibration solution at a certain level which depends on the identification information obtained via the class information setting portion; a correction relation calculation portion configured to receive a cavitation level signal of a standard handpiece and a cavitation level signal of another handpiece and to calculate a correction relation of the other handpiece with respect to the standard handpiece from a comparison relation of the cavitation level signal of the other handpiece with respect to the cavitation level signal of the standard handpiece; a condition storage portion which, when a relation between a strength of the drive signal applied to the ultrasound transducer of the handpiece (40; 40X) and an actual vibration strength at the distal end portion of the handpiece (40; 40X) is regarded as calibration information, determines calibration information of the other handpiece with respect to calibration information of the standard handpiece based on the correction relation calculated by the correction relation calculation portion, and stores the calculated calibration information; and a control portion configured to control the drive signal to be supplied from the drive portion to the ultrasound transducer, wherein the drive signal is obtained by correcting a standard drive signal using the calibration information of the other handpiece stored in the condition storage portion, in order to cause the distal end portion to have a vibration strength suited for coagulation procedure or dissection procedure of a living tissue. a class information setting portion which, when connected to the handpiece (40; 40X), causes an electric signal to be transmitted from the class information storage portion to set the identification information; a drive portion which is connected to the ultrasound transducer and supplies the ultrasound transducer with a drive signal for generating the ultrasound vibrations; a detection portion configured to detect a signal level where only frequency components obtained by removing a resonance frequency of the drive signal are acquired, the signal level being a level of a cavitation level signal, the signal level corresponding to a state that the distal end portion is vibrated with ultrasound by a drive signal that causes vibration amplitude for calibration for causing the distal end portion of the probe to generate cavitation in a calibration solution at a certain level which depends on the identification information obtained via the class information setting portion; a correction relation calculation portion configured to receive a cavitation level signal of a standard handpiece and a cavitation level signal of another handpiece and to calculate a correction relation of the other handpiece with respect to the standard handpiece from a comparison relation of the cavitation level signal of the other handpiece with respect to the cavitation level signal of the standard handpiece; a condition storage portion which, when a relation between a strength of the drive signal applied to the ultrasound transducer of the handpiece (40; 40X) and an actual vibration strength at the distal end portion of the handpiece (40; 40X) is regarded as calibration information, determines calibration information of the other handpiece with respect to calibration information of the standard handpiece based on the correction relation calculated by the correction relation calculation portion, and stores the calculated calibration information; and a control portion configured to control the drive signal to be supplied from the drive portion to the ultrasound transducer, wherein the drive signal is obtained by correcting a standard drive signal using the calibration information of the other handpiece stored in the condition storage portion, in order to cause the distal end portion to have a vibration strength suited for coagulation procedure or dissection procedure of a living tissue.