The present invention relates to an ultrasonic nonlinearity measuring method generated by a high voltage pulser and more specifically, includes a calibration step of transmitting and receiving an ultrasonic signal to and from an object to be inspected having a reception probe attached thereto, by a receiving unit; a harmonic wave measuring step of transmitting a tone burst signal to an object to be inspected having a transmission/reception probe attached thereto and receiving the tone burst signal which passes through the object to be inspected, by the receiving unit; a harmonic wave measuring step of transmitting a tone burst signal to an object to be inspected having a transmission probe attached thereto and receiving the transmitted tone burst signal, by a transmitting unit; a calibration step of transmitting and receiving an ultrasonic signal to and from an object to be inspected having a transmission probe attached thereto, by the transmitting unit; and a step of measuring an ultrasonic nonlinearity of the object to be inspected by comparing a fundamental frequency and a harmonic component measured by the receiving unit and a fundamental frequency and a harmonic component measured by the transmitting unit.