The clutter reduction effect by adaptive beamforming is homogeneously obtained in the entire image even in the imaging conditions in which the number of bundles of signals has a large distribution in the ultrasonic imaging image.The received signal processing unit determines the coherence value between a plurality of received signals for a predetermined imaging point, or an addition part for bundling a plurality of signals after processing the received signal, and a plurality of signals to be added by the addition part, and by adding the weight corresponding to the coherence value A plurality of signals before being added by the arithmetic unit or a weighting portion for weighting the signal after addition in the adding unit.The weighting portion weighs the coherence value non linearly for a predetermined direction in the subject and uses a non-linear weighted coherence value to add a plurality of signals prior to being added in the summing portion or by adding the summed signal to the summing portion .信号の束ね数が、超音波撮像画像中で大きく分布を持つような撮像条件においても、適応ビームフォーミングによるクラッタ低減効果を画像全体に均質に得る。 受信信号処理部は、所定の撮像点についての複数の受信信号、または、受信信号を処理後の複数の信号を束ねる加算部と、加算部で加算する複数の信号間のコヒーレンス値を求め、コヒーレンス値に応じた重みによって加算部で加算される前の複数の信号、または、加算部で加算後の信号を重み付けする重み付け部を備えている。重み付け部は、コヒーレンス値を、被検体における所定の方向について非線形に重み付けし、非線形に重み付けされたコヒーレンス値を用いて、加算部で加算される前の複数の信号、または、加算部で加算後の信号を重み付けする。
