To provide a method and an apparatus for easily measuring the strength of an ultrasonic wave at a low cost.

The apparatus 11 for measuring the strength of an ultrasonic wave includes a dust generator 22 immersed in a cleaning liquid 13, an oscillator 17 that causes the dust generator 22 to vibrate by virtue of an ultrasonic wave to be measured to disperse the particles detached from the dust generator 22 into the cleaning liquid 13, a counter 21 that counts the number of the particles present in the cleaning liquid 13, and a calculator 45 that calculates the strength of the ultrasonic wave to be measured based on the number of the particles counted. Thus, the strength of an ultrasonic wave can easily be measured at a low cost without using a sound pressure meter.