To suppress reduction of spatial resolution and S/N ratio regardless of the depth of an observation point in a synthetic aperture method.SOLUTION: An ultrasonic signal processing device comprises: a transmission unit that repeats a transmission event of selecting some of a plurality of vibrators as a transmission vibrator column and transmitting an ultrasonic beam to an ultrasonic main radiation region, while shifting a transmission aperture in a direction in which the vibrators are arranged for each transmission event； a reception unit that generates a received signal column； a phasing addition unit that sets, in the ultrasonic main radiation regions, an object region with a shape which has a decreasing width of arrangement of the vibrators as a depth is shallower in a depth range positioned at a shallower position than a focus point, and for a plurality of observation points in the object region, phasing-adding the received signal column on the basis of a reflected ultrasonic wave obtained from each observation point, thus generating a sub-frame acoustic line signal； and a combining unit that generates a frame acoustic line signal on the basis of the plurality of sub-frame acoustic line signals.SELECTED DRAWING: Figure 5【課題】合成開口法において、観測点の深度に係らず空間分解能及びＳ／Ｎ比の低下を抑制する。【解決手段】超音波信号処理装置であって、複数の振動子の一部を送信振動子列として選択して超音波主照射領域に超音波ビームを送信させる送信イベントを、送信開口を送信イベントごとに振動子の並ぶ方向にシフトしながら繰り返す送信部と、受信信号列を生成する受信部と、フォーカス点よりも浅部に位置する深度範囲において深度が浅いほど振動子の並ぶ方向の幅が小さくなる形状を有する対象領域を超音波主照射領域内に設定し、対象領域の複数の観測点について、各観測点から得られた反射超音波に基づく前記受信信号列を整相加算してサブフレーム音響線信号を生成する整相加算部と、複数のサブフレーム音響線信号に基づき、フレーム音響線信号を生成する合成部とを備える。【選択図】図５
