A flow metering method and a flowmeter capable of providing an electric output corresponding to the metered flow rate of metered fluid by an electric circuit including a thermal type flow sensor disposed in a metering flow path and an electric output corresponding to the reference flow rate of the metered fluid by an electric circuit including a reference thermal type flow sensor disposed in a reference flow path allowing the metered flow to flow freely; the flow metering method, comprising the steps of providing a calibration curve including a reference flow calibration curve and a measurement flow calibration curve at a plurality of temperatures for reference fluid beforehand, providing the deviated amount of the temperature of the reference flow calibration curve from the reference temperature corresponding to the electric output based on the electric output corresponding to the reference flow calibration curve based on the deviated amount, and converting the temperature corrected amount to the flow value of the metered fluid based on the electric output corresponding to the metered flow rate of the metered fluid by using the measured flow rate calibration curve of the reference temperature and by allowing for the temperature corrected amount.