An ultrasonic testing device having a packaged semiconductor device as a testing target, the device including: an ultrasonic oscillator disposed to face the semiconductor device; a pulse generator generating a driving signal that is used in the generation of an ultrasonic wave to be output from the ultrasonic oscillator; and an analysis unit analyzing an output signal that is output from the semiconductor device in accordance with the irradiation of the ultrasonic wave from the ultrasonic oscillator, in which the pulse generator sets an optimal frequency of the driving signal such that the absorption of the ultrasonic wave in the semiconductor device is maximized.