In a sphygmomanometer, a value representing a perimeter of a measuring portion is obtained. A parameter for controlling a drive voltage of a pump is determined based on the value. The drive voltage is determined based on the parameter and an internal pressure of a fluid bladder to pressurize the fluid bladder. In pressurizing process, a diastolic blood pressure value is calculated. A systolic blood pressure value is estimated, and when the internal pressure of the fluid bladder reaches the pressure, the pressurizing is stopped. A gap of a valve for discharging the fluid from the fluid bladder is determined based on a perimeter of a measuring portion, and the fluid bladder is depressurized with the gap constant. In the depressurizing process, the systolic blood pressure value is calculated. When the systolic blood pressure value is calculated, the fluid is discharged from the fluid bladder, and the measurement is terminated.
