A method of driving a pump, the method being used in a pressure-applying apparatus (10; 12) including: a flow passage (22, 24); a pump configured to impart pressure into the flow passage (22, 24); an opening and closing valve that is disposed in the flow passage (22, 24), and that is configured to open and close the flow passage (22, 24); a pressure detector configured to detect pressure in the flow passage (22, 24); and an atmospheric air open valve that is disposed in the flow passage (22, 24), and that is configured to open an interior of the flow passage (22, 24) to atmospheric air, and the method comprising: closing the opening and closing valve and opening the atmospheric air open valve, and then driving the pump; closing the atmospheric air open valve while continuing to drive the pump; evaluating a state of the pump based on an arithmetic mean of the pressure detected by the pressure detector, by stopping the pump at a time at which a predetermined time period has elapsed after closing the atmospheric air open valve, detecting the pressure more than once by the pressure detector and obtaining the arithmetic mean of the plurality of measured pressure values; and adjusting a driving condition of the pump, based on the state of the pump, as evaluated by the evaluating the state of the pump based on the arithmetic mean of the pressure. a flow passage (22, 24); a pump configured to impart pressure into the flow passage (22, 24); an opening and closing valve that is disposed in the flow passage (22, 24), and that is configured to open and close the flow passage (22, 24); a pressure detector configured to detect pressure in the flow passage (22, 24); and an atmospheric air open valve that is disposed in the flow passage (22, 24), and that is configured to open an interior of the flow passage (22, 24) to atmospheric air, and the method comprising: closing the opening and closing valve and opening the atmospheric air open valve, and then driving the pump; closing the atmospheric air open valve while continuing to drive the pump; evaluating a state of the pump based on an arithmetic mean of the pressure detected by the pressure detector, by stopping the pump at a time at which a predetermined time period has elapsed after closing the atmospheric air open valve, detecting the pressure more than once by the pressure detector and obtaining the arithmetic mean of the plurality of measured pressure values; and adjusting a driving condition of the pump, based on the state of the pump, as evaluated by the evaluating the state of the pump based on the arithmetic mean of the pressure. closing the opening and closing valve and opening the atmospheric air open valve, and then driving the pump; closing the atmospheric air open valve while continuing to drive the pump; evaluating a state of the pump based on an arithmetic mean of the pressure detected by the pressure detector, by stopping the pump at a time at which a predetermined time period has elapsed after closing the atmospheric air open valve, detecting the pressure more than once by the pressure detector and obtaining the arithmetic mean of the plurality of measured pressure values; and adjusting a driving condition of the pump, based on the state of the pump, as evaluated by the evaluating the state of the pump based on the arithmetic mean of the pressure.