A pressurizing/depressurizing section (3) increases or decreases an internal pressure of a cuff (20). A first controlling section (4) controls an operation of the pressurizing/depressurizing section (3) so as to cause the internal pressure to transit from a pressure transient state to a pressure steady state and vice versa. A detecting section (5) detects the internal pressure. A storage section (6) stores control modes ways for increasing/decreasing the internal pressure of which are different. A determining section (7) determines a type of the cuff (20) in accordance with whether the detected internal pressure has reached the pressure steady state within a predetermined time period since start of the pressure transient state. A second controlling section (9) selects one of the control modes in accordance with the determined type of the cuff (20), and to control the operation of the pressurizing/depressurizing section (3) in accordance with the selected one of the control modes.
