A maximum voltage value, a minimum voltage value, and one beat time in a pressure change of a pulse wave are measured based on a voltage value of a blood vessel pulse wave signal measured by a first pressure sensor, and a second pressure Pressure is applied to the blood vessel via the sensor and the skin and pressurization is stopped when pressure is applied to measure the blood vessel pulse wave signal and the pressure value of the stress is applied to the blood vessel at a predetermined first decompression rate . When the blood vessel pulse wave signal is measured, the pressure value of the second pressure sensor immediately before that is measured as the maximum blood pressure value, the pressure value of the stress is decompressed with respect to the blood vessel at a predetermined second decompression rate, When the pressure value is reduced at a predetermined third decompression rate and a blood vessel pulse wave signal having a voltage value of a steady pulse wave is measured, the pressure value of the second pressure sensor at that time is measured as the minimum blood pressure value.第1の圧力センサにより測定された血管脈波信号の電圧値に基づいて、脈波の圧力変化における最大電圧値と最小電圧値と1拍時間とを測定し、圧力印加機構により第2の圧力センサ及び皮膚を介して血管に対して応力を印加して加圧して血管脈波信号を測定しなくなったとき加圧を停止し、血管に対して応力の圧力値を所定の第1の減圧速度で減圧する。血管脈波信号を測定したとき、その直前の第2の圧力センサの圧力値を最大血圧値として測定し、血管に対して応力の圧力値を所定の第2の減圧速度で減圧し、応力の圧力値を所定の第3の減圧速度で減圧し、定常脈波の電圧値を有する血管脈波信号を測定したとき、そのときの第2の圧力センサの圧力値を最小血圧値として測定する。
