<p>A device for measuring the blood pressure information includes a servo control section (106) which performs servo control of a pressure regulation unit (50) so that the value of an arterial volume signal matches a control target value, and a variation detection section (110) which detects an abrupt variation in the arterial volume signal in the initial stage during the servo control period. The variation detection section decides that an abrupt variation has occurred when the control deviation representing the level of the arterial volume signal with reference to the control target value becomes more than a predetermined ratio of the reference deviation. The device for measuring the blood pressure information is further provided with a regulation section (112) which regulates the control amount of the pressure regulation unit by the servo control section so that there is no excessive response when the variation detection section detects an abrupt variation.</p>
