An ultrasound diagnostic apparatus for measuring the characteristics of a carotid artery blood vessel, wherein a long axis of the carotid artery is based on a transmission / reception processing unit that transmits / receives ultrasound to / from the carotid artery and received signals of a cross section of the carotid artery at a plurality of positions A short-axis cross-sectional image generator that generates a plurality of short-axis cross-sectional images showing a short-axis cross-section perpendicular to the direction, and a specification including a short-axis cross-section of the internal carotid artery and the external carotid artery among the plurality of short-axis cross-sectional images In a plane parallel to the short-axis cross section of the carotid artery based on the short-axis cross-section image selection unit for selecting the short-axis cross-section image and the coordinate position of the short-axis cross-section of the internal carotid artery and external carotid artery in the specific short-axis cross-section image And a relative angle calculation unit for calculating a relative angle of the probe with respect to the carotid artery.頸動脈の血管壁の特性を計測する超音波診断装置であって、頸動脈に対し超音波の送受信行う送受信処理部と、複数位置における頸動脈の断面の受信信号に基づき、頸動脈の長軸方向と垂直な短軸断面を示す複数の短軸断面画像を生成する短軸断面画像生成部と、複数の短軸断面画像のうち、内頸動脈及び外頸動脈の短軸断面が含まれる特定短軸断面画像を選択する短軸断面画像選択部と、特定短軸断面画像における、内頸動脈及び外頸動脈の短軸断面の座標位置に基づき、頸動脈の短軸断面と平行な平面内における探触子の頸動脈に対する相対角度を算出する相対角度算出部とを備えた。
