The method of calculating the degree of arteriosclerosis index in the blood pressure information measurement apparatus and the apparatus

Measuring device receives an input of a change in the internal pressure of the air bag attached to the measurement site, to identify the one heartbeat of the blood pressure waveform from the pressure waveform (S101). Identifying a maximum amplitude of the maximum amplitude and the reflected wave of the ejection wave of one beat blood pressure waveform, and calculates an AI value by calculating the ratio (S103). The measuring device in advance correspondence relationships between AI and threshold values ​​are stored, based thereon, calculates a threshold value for detecting a rising point of the reflected wave (S105). The time of reaching the amplitude obtained by multiplying the threshold to the maximum amplitude of the reflected wave of the blood pressure wave as a rising point of the reflected wave is identified as a feature point for Tr calculated (S107).