As different artery blood pressure combination measurement, peripheral blood pressure combination measurement that combines blood vessel diameter measurement to measure a blood vessel diameter as a blood vessel cross-section index value of a central artery as a first artery with peripheral blood pressure measurement to measure blood pressure of a peripheral artery as a second artery is conducted. Then, a parameter for a blood pressure estimation process (for example, a blood vessel hardness parameter or a correlation parameter) that estimates the central aortic blood pressure from the blood vessel diameter of the central artery is corrected by using measurement results of the peripheral blood pressure combination measurement.