The present invention relates to an air flowmeter in which an air flow rate sensing element and air temperature sensing element are integrated with each other and mounted on a substrate and at the same time the fluid temperature sensing element is formed on a diaphragm, the fluid flowmeter being capable of measuring a fluid flow rate with high accuracy by suppressing the self-heating of the fluid temperature sensing element.
In the invention, an air temperature sensor 11 sensing an air temperature, supplied with a pulse signal as a driving signal from a pulse signal source 19, senses an air temperature based on the pulse signal. While the air temperature sensor 11 is self-heated during an electrical current supplying time period by the pulse signal, it is cooled during an electrical current halting time period. Accordingly, the self-heating of the air temperature sensor 11 by the driving signal is suppressed, and a thermal effect on air flow rate sensing elements 5 to 10 disposed in an air flow downstream side of the air temperature sensor 11 is also reduced.