Because isochronism to be high the compound picture which is strong in being off-center is actualized, the picture is formed with the sending and receiving beam former output which has the point image function where direction of plural wave number vectors differs.等時性が高くぶれに強いコンパウンド画像を実現するため、複数の波数ベクトルの方向の異なる点像関数を持つ送受信ビームフォーマ出力で画像を構成する。