A CPU detects pulse waves in a pressure signal of a cuff detected during a period of reducing pressure applied by the cuff to a measurement site and acquires blood flow sound signals corresponding to blood flow sounds occurring in the pressure reduction period. Then, data for a pulse wave envelope that associates the amplitude values of the detected pulse waves with the pressurizing pressures at the pulse wave generation times, and data for a blood flow sound envelope that associates the amplitude values of the blood flow sound signals with the pressurizing pressures at the blood flow sound generation times are generated, and the data for the pulse wave envelope and the data for the blood flow sound envelope are used to determine whether or not there is periodic variation in the blood pressure during the pressure reduction period.
