Ultrasonic Testing Method

An ultrasonic testing method, the method comprising the steps of:

• causing a transverse ultrasonic wave to be incident on a test object that has acoustic anisotropy and is constituted by a crystal structure, in a direction perpendicular to a surface of the test object;
• and
• measuring a thickness of the test object on the basis of a velocity of the transverse ultrasonic wave propagating in the test object and a time period for the propagation of the transverse ultrasonic wave, while using, as the time period for the propagation of the transverse ultrasonic wave, a time period for propagation of a transverse wave component that propagates in the test object for the shortest time period, among a plurality of transverse wave components that are obtained by dividing the transverse ultrasonic wave and have polarizations in the different directions (vibration direction) due to the acoustic anisotropy.