Provided is a flowmeter with a flow tube through which fluid flows; a cooling apparatus adapted to cool a part of the flow tube; a first temperature detecting section for detecting the temperature of the flow tube cooled by the cooling apparatus; a second temperature detecting section for detecting the temperature of the cooling apparatus; a third temperature detecting section for detecting the temperature of a non-cooling area upstream of a cooling area in the flow tube; and an information processing section, which controls the cooling apparatus make a difference between the temperature detected by the second temperature detecting section and the temperature detected by the third temperature detecting section to be a prescribed value, and calculates the flow rate of the fluid flowing in the flow tube.