even if body motion is generated of which is capable of continuous measurement living body of vessel diameter and blood vessel to provide a diameter continuous measurement equipment. Displacement of the feature point region R around the plurality of feature points P in a short-axis images are repeatedly generated based on the ultrasonic reflection signal is sequentially determined by the pattern matching, the blood vessel 12 from the displacement of the plurality of feature points region R the diameter change amount is sequentially calculated, the time-series change of blood vessel diameter is measured on the basis of the diameter change of the vessel 12, the living body such as the by the ultrasonic sensor of the short axis image hardly affected by displacement motion time-series change in the diameter of blood vessels I obtained.体動が発生しても血管径の連続測定が可能な生体の血管径連続測定装置を提供する。超音波反射信号に基づいて繰り返し生成された短軸画像間における複数の特徴点Pの周囲の特徴点領域Rの変位がパターンマッチングにより逐次求められ、それら複数の特徴点領域Rの変位から血管12の径変化量が逐次算出され、その血管12の径変化量に基づいて血管径の時系列的変化が測定されるので、体動などによる超音波センサのずれに影響され難い短軸画像から生体の血管の径の時系列的変化が得られる。
