A pump device and method for stabilizing a suction flow rate irrespective of an outside air temperature. The method includes: outputting a drive signal for driving a motor at a rotation speed for discharging gas of the reference flow rate from the suction port of the pump main body; measuring a temperature of gas discharged from the suction port or a temperature of the pump main body by a temperature sensor attached to the pump main body; calculating an actual flow rate of the gas discharged from the suction port based on a temperature signal relating to the temperature of the gas included in an output of the temperature sensor; and correcting the drive signal such that the actual flow rate equals the reference flow rate and outputting the corrected drive signal to the motor.