In an ultrasonic blood pressure meter 1, changes in blood pressure in a peripheral artery measured by a blood pressure meter 2 are input from an input unit 40. A blood vessel diameter measuring unit 120 measures changes in the blood vessel diameter of a central artery using ultrasound. A calibrating unit 130 calibrates a parameter related to a blood pressure estimation process for estimating central blood pressure from the blood vessel diameter of the central artery, using results of measurement by the blood pressure meter 2 and the blood vessel diameter measuring unit 120 during a given correspondence period, of a one-heartbeat period, in which the relationship between the blood vessel diameter of the central artery and the blood pressure in the peripheral artery corresponds to the relationship between the blood vessel diameter of the central artery and the central blood pressure.
