To increase reliability of a measurement result in a measurement of an ultrasound elasticity modulus.SOLUTION: An ultrasound diagnostic apparatus causes transmission of a push wave to detect a propagation velocity of a shear wave generated by an acoustic radiation pressure of the push wave, comprising: a push wave pulse transmission unit for transmitting a push wave which converges to one or more transmission focus points in a subject； a detection wave pulse transmission unit for transmitting a detection wave, which passes through a region of interest within the subject, multiple times, following transmission of the push wave； a displacement detection unit for detecting a displacement amount of a tissue at each of a plurality of observation points in the region of interest on the basis of a reflection of each detection wave received in a time series in correspondence with multiple transmission of the detection wave； an analysis target determination unit for determining an analysis target region, in which the propagation of the shear wave is analyzed, on the basis of steepness of temporal variation of the displacement amount； and a propagation information analysis unit for calculating the propagation velocity of the shear wave at each observation point in the analysis target region on the basis of the displacement of the tissue at the plurality of observation points in the analysis target region.SELECTED DRAWING: Figure 1【課題】超音波弾性率計測において、弾性率計測結果の信頼性を向上させる。【解決手段】プッシュ波を送信させ、プッシュ波の音響放射圧により生じたせん断波の伝播速度を検出する超音波診断装置であって、被検体内の１以上の送信焦点に集束するプッシュ波を送信させるプッシュ波パルス送信部と、プッシュ波の送信に続き、被検体内の関心領域を通過する検出波を複数回送信させる検出波パルス送信部と、複数回の検出波の各々に対応して時系列に受信された反射検出波に基づき、関心領域内の複数の観測点それぞれにおける組織の変位量を検出する変位検出部と、変位量の時間変化の急峻度に基づき、せん断波の伝播解析の対象となる解析対象領域を決定する解析対象決定部と、解析対象領域内に存在する複数の観測点における組織の変位量に基づいて、解析対象領域内に存在する観測点それぞれにおけるせん断波の伝播速度を算出する伝播情報解析部とを備える。【選択図】図１
