A method of driving a pump in a pressure-applying apparatus (10; 12) used to stir a sample diluted with a dilution liquid prior to the diluted sample being filled into a capillary formed in an analysis tool, the pump 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; measuring a pressure in the flow passage (22, 24) by the pressure detector more than once; estimating a time at which an increase in the pressure in the flow passage (22, 24) started based on a change of measurement value with respect to time, wherein the time between the time of closing the atmospheric air open valve and a time of starting an increase in the pressure in the flow passage (22, 24) is a time lag Δt; and evaluating a state of the pump, based on: the pressure detected by the pressure detector at a time at which, after closing the atmospheric air open valve, the time lag Δt has elapsed and then a predetermined time period t1 has elapsed while continuing to drive the pump. 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; measuring a pressure in the flow passage (22, 24) by the pressure detector more than once; estimating a time at which an increase in the pressure in the flow passage (22, 24) started based on a change of measurement value with respect to time, wherein the time between the time of closing the atmospheric air open valve and a time of starting an increase in the pressure in the flow passage (22, 24) is a time lag Δt; and evaluating a state of the pump, based on: the pressure detected by the pressure detector at a time at which, after closing the atmospheric air open valve, the time lag Δt has elapsed and then a predetermined time period t1 has elapsed while continuing to drive the pump. 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; measuring a pressure in the flow passage (22, 24) by the pressure detector more than once; estimating a time at which an increase in the pressure in the flow passage (22, 24) started based on a change of measurement value with respect to time, wherein the time between the time of closing the atmospheric air open valve and a time of starting an increase in the pressure in the flow passage (22, 24) is a time lag Δt; and evaluating a state of the pump, based on: the pressure detected by the pressure detector at a time at which, after closing the atmospheric air open valve, the time lag Δt has elapsed and then a predetermined time period t1 has elapsed while continuing to drive the pump.