PURPOSE: To positively set a gate for a target reflection wave.

CONSTITUTION: First and second ultrasonic vibrators V1 and V2 for generation two types of ultrasonic waves, namely longitudinal and transverse waves by excitation signals are provided and the first and second ultrasonic vibrators V1 and V2 are excited so that a timing when the reflection waves from a sample 16 propagating inside an acoustic lens 14e in the form of longitudinal waves are received by the ultrasonic vibrator V2 and a timing when the reflection waves from the sample 16 propagating inside the acoustic lens 14e in the form of transverse waves are received by the first ultrasonic vibrator V1 are nearly simultaneous. Then, by applying a synthesis reception signal to a crate after a time which is equal to the time difference between the round trips of the longitudinal and transverse waves within the acoustic lens 14e passes from the timing when the reflection wave from the sample 16 propagating in the acoustic lens 14e in the form of longitudinal waveforms is received by the first ultrasonic vibrator v., the synthesis signal of the reflection waves from the sample 16 received nearly simultaneously by the first and second ultrasonic vibrators V1 and V2 is taken out.