1. An ultrasonic inspection method comprising the steps of: preparing an ultrasonic probe having a plurality of piezoelectric elements; scanning an inspection object with the ultrasonic probe having the plurality of piezoelectric elements according to a scanning method; receiving ultrasonic waves from the inspection object with the ultrasonic probe having the plurality of piezoelectric elements; generating three-dimensional ultrasonic inspection data from waveforms of the ultrasonic waves received by the ultrasonic probe; calculating a plurality of ultrasonic propagation data on the basis of three-dimensional shape data of the inspection object and the scanning method by sequentially changing ultrasonic wave incident points and ultrasonic wave incident directions; comparing the three-dimensional ultrasonic inspection data with the plurality of ultrasonic propagation data to match a combination of the three-dimensional ultrasonic inspection data with a portion of the plurality of ultrasonic propagation data; and displaying the three-dimensional ultrasonic inspection data and the three-dimensional shape data in such a manner as to move on a display screen a position at which to display the three-dimensional ultrasonic inspection data or the three-dimensional shape data on the basis of the combination of the three-dimensional ultrasonic inspection data and the portion of the ultrasonic propagation data which match each other.