A plurality of signal transmitters are respectively configured to produce a pulse current by repeatedly switching the connection state of a switching element. A plurality of ultrasonic transducers are respectively configured to transmit an ultrasonic pulse to a subject to be examined upon receiving said pulse current, and to produce a receiving current upon receiving the reflected wave. A signal receiver is configured to receive said receiving current. A test signal generator is configured to produce a test signal and to output said test signal to a connection point of said signal transmitter, said ultrasonic transducer, and said signal receiver by switching said connection state of said switching element to a state through which said test signal is conducted.