Without using an approximate wavefront propagation model, an appropriate delay time is set for the received signal both inside and outside the irradiated region of the transmission beam to obtain a phasing signal. The reception beamformer includes a wavefront propagation calculation unit 121 that calculates the time required for ultrasonic waves transmitted from a plurality of ultrasonic elements to reach the reception focal point, and a plurality of ultrasonic elements calculated by the wavefront propagation calculation unit 121. A delay time extraction unit 122 that calculates a delay time for the reception focus based on the distribution of arrival times of the ultrasonic waves. Therefore, even when the wavefront reaching the reception focal point has a complicated shape, it is not necessary to approximate the wavefront, and the phasing addition is performed with an appropriate delay time obtained from the time when the ultrasonic wave reaches the reception focal point. It can be carried out.近似的な波面伝搬モデルを用いることなく、送信ビームの照射領域の内外ともに受信信号に適切な遅延時間を設定して整相信号を得る。 受信ビームフォーマは、複数の超音波素子から送信される超音波がそれぞれ、受信焦点に到達する時間を演算により求める波面伝搬演算部１２１と、波面伝搬演算部１２１が求めた複数の超音波素子毎の超音波の到達時間の分布に基づいて受信焦点についての遅延時間を算出する遅延時間抽出部１２２とを含む。よって、受信焦点に到達する波面が複雑な形状となる場合であっても、波面を近似する必要がなく、超音波がその受信焦点に到達する時間から求めた適切な遅延時間によって整相加算を行うことができる。
