Ultrasonic signal processing method according to one embodiment by the frame present invention, when creating an ultrasonic image of the sequential execution to one frame of ultrasonic transmission of at least once for each of a plurality of transmission focusing line , acquired in a plurality of transmission focusing line along ultrasonic transmission N times (N is an integer of 2 or more) out of different transmission focus lines along ultrasonic transmission M times (M is less than 1 or more N integer) measuring the sound velocity within the object based on the transmitted and received data.本発明の一態様に係る超音波信号処理方法は、複数の送信フォーカスラインそれぞれに対して少なくとも1回ずつ超音波の送信を順次実行して1フレームの超音波画像を作成する場合に、複数の送信フォーカスラインに沿う超音波の送信N回(Nは2以上の整数)のうちの異なる送信フォーカスラインに沿う超音波の送信M回(Mは1以上N未満の整数)において取得した送受信データに基づいて被検体内の音速を測定する。
