PROBLEM TO BE SOLVED: To provide a method of deriving a highly accurate blood pressure value which is not easily affected by the individual difference of a person to be measured.SOLUTION: The blood pressure measuring apparatus is provided with: a cuff part a pressure control means for pressurizing or reducing the respective air bags of the cuff part a pressure sensor for detecting a pressure inside each air bag a means for extracting pulse wave signals superimposed on the pressure inside a cuff detected by the pressure sensor in the process of pressurizing or reducing each air bag of the cuff part and a blood pressure value deriving means for deriving a systolic pressure value and/or a diastolic pressure value on the basis of the change of the feature amount of the pulse wave signals and the pressure inside the cuff at the point of time of the change. The blood pressure value deriving means detects the maximum gradient point of one cycle pulse wave in the period of the peak point of a one cycle pulse wave signal included in the time sequential data of the pulse wave signal and a bottom point which appear preceding the peak point, and derives the systolic pressure value and/or the diastolic pressure value on the basis of a difference value between a pulse wave amplitude value at the bottom point which appears preceding the maximum gradient point and a value at the time at the bottom point of a tangent passing through the maximum gradient point.COPYRIGHT: (C)2009,JPO&INPIT【課題】非測定者の個体差に影響されにくい精度の高い血圧値の導出手法を提供する。【解決手段】血圧測定装置において、カフ部と、カフ部の各空気袋を加圧または減圧する圧力制御手段と、各空気袋内の圧力を検出する圧力センサと、カフ部の各空気袋を加圧または減圧する過程において、圧力センサにより検出されるカフ内の圧力に重畳した脈波信号抽出手段と、脈波信号の特徴量の変化と当該変化時点でのカフ内の圧力とに基づき、収縮期血圧値及び/又は拡張期血圧値を導出する血圧値導出手段とを備え、血圧値導出手段は、脈波信号の時系列データに含まれる1周期脈波信号の、ピーク点と該ピーク点に先行して現れるボトム点との期間での1周期脈波の最大勾配点を検出し、最大勾配点に先行して現れるボトム点における脈波振幅値と最大勾配点を通過する接線の前記ボトム点における時刻での値との差値に基づいて収縮期血圧値及び/又は拡張期血圧値を導出する。【選択図】図10
