Method and apparatus for measurement of thickness utilizing ultrasonic pulses

Method and apparatus are disclosed for measurement of the thickness of a workpiece by periodically transmitting ultrasonic pulses into a workpiece by means of a probe provided at its front surface with a delay material, receiving ultrasonic echo pulses reflected from the bottom surface of the workpiece, measuring the period of time corresponding to the period of time elapsed from the transmission of each ultrasonic pulse to the reception of its related echo pulse minus the period of time corresponding to the propagation time of the ultrasonic pulse through the delay material which is specified by the setting of a zero-point adjusting circuit, calculating the thickness of the workpiece from such measured time periods, and displaying the thickness value thus calculated on a display. The setting of the zero-point adjusting circuit is carried out by adjusting the setting of the zero-point adjusting circuit so that the value displayed on the display becomes substantially zero while keeping the probe separated from the workpiece.