PROBLEM TO BE SOLVED: To provide an automatic blood pressure measuring apparatus capable of obtaining an accurate pulse wave by properly applying compression pressure to an artery in a compressed portion, and obtaining a highly accurate highest blood pressure value based on the pulse wave.SOLUTION: When a first signal ratio that is a ratio of a sampling value of an intermediate inflation bag 24 to a sampling value of a first pulse wave signal SM1 from an upstream side inflation bag 22 exceeds a first signal ratio change determination value, and a second signal ratio that is a ratio of a sampling value of a third pulse wave signal from a downstream side inflation bag 26 to a sampling value of a second pulse wave signal from the intermediate inflation bag 24 exceeds a second signal ratio change determination value, a highest blood pressure value is determined based on compression pressure at that time. A highly accurate highest blood pressure value can be obtained based on the first signal ration and the second signal ration between pulse wave signals SM.SELECTED DRAWING: Figure 12【課題】被圧迫部位内の動脈に圧迫圧力を適正に加えることで正確な脈波が得られ、その脈波に基づいて精度の高い最高血圧値が得られる自動血圧測定装置を提供する。【解決手段】上流側膨張袋２２からの第１脈波信号ＳＭ１のサンプリング値に対する中間膨張袋２４のサンプリング値の比である第１信号比が第１信号比変化判定値を超え、且つ、中間膨張袋２４からの第２脈波信号のサンプリング値に対する下流側膨張袋２６からの第３脈波信号のサンプリング値の比である第２信号比が第２信号比変化判定値を超えたときに、そのときの圧迫圧力に基づいて最高血圧値が決定される。それら脈波信号ＳＭ間の第１信号比、第２信号比に基づいて精度の高い最高血圧値が得られる。【選択図】図１２
