PURPOSE: To cope with the high frequency diagnosis and the low frequency diagnosis with a piece of probe by transmitting an ultrasonic wave having plural frequencies, and switching a receiving system so that a Doppler signal corresponding to each frequency can be received selectively at the time of reception.

CONSTITUTION: By respective transmitting vibrators 5a, 5b of a probe 10 of a transmitting system A, a low frequency and a high frequency are generated, and transmitted to a body to be examined. Subsequently, when a Doppler signal is received in a receiving system B1, in the case it is desired to diagnosis such a low blood flow speed part as the mammary gland, a first receiving system B1 is selected by a switching circuit 11. Thus, a first receiving system B1 receives a Doppler signal corresponding to low frequency transmission, and detects a low blood flow speed by an excellent characteristic from a shallow part area. On the other hand, at the time of executing a diagnosis excellent in S/N, a second receiving system B2 is selected by a switching circuit 11. In such a manner, a second receiving system B2 receives a Doppler signal corresponding to high frequency transmission, and can detect a high blood flow speed with high S/N from a high blood flow speed part of such a deep area as the heart.