A belt to be mounted around a measurement site； first pulse wave sensor and second pulse wave sensor mounted on the belt, separated from each other, configured to detect pulse waves in an artery passing through the measurement site； and pressing member mounted on the belt, capable of pressing first pulse wave sensor and second pulse wave sensor against the measurement site while varying pressing force. Time difference between first and second pulse wave signals is acquired as pulse transit time. Blood pressure is calculated based on the pulse transit time acquired by the measurement processing unit by using a predetermined correspondence equation between pulse transit time and blood pressure. Pulse transit time is acquired with the measurement processing unit while pressing force by pressing member is changed in resting state, and corresponding equation is calibrated based on plurality of pulse transit times corresponding to plurality of respective pressing forces.
