Ultrasonic Test Method And Ultrasonic Test Instrument Used For The Method

An ultrasonic test method for detecting a defective portion more precisely in a noncontact reflection way, and ultrasonic test instrument used for the method. An ultrasonic wave is transmitted from a transmitter ( 20 ( 21 )) provided on one side of an object under test, and the reflected wave is received by a receiver ( 30 ( 31 )) provided on the same side. The ultrasonic wave is transmitted/received through an air layer between the transmitter and the object ( 100 ) under test and between the receiver and the object ( 100 ). The relative positions of the transmitter ( 20 ), the receiver ( 30 ), and the object ( 100 ) are so determined that the air propagation time ta of the air path (RA) between the transmitter and the receiver is longer than the propagation time tb of the reflected wave in the reflection path (RB). The propagation of the ultrasonic wave through the solid body between the transmitter and the receiver is blocked. This invention is suitable to test laminated material ( 100 ) such as a laminate of CFRP ( 101 ) and insulation ( 102 ) in a noncontact way.