<p>A thermal air flowmeter which improves air flow rate measurement sensitivity, reduces power consumption of a heating element and broadens the measuring range. A heating resistor (4) is provided on insulating film (6) in a thermal insulating area as a rectangular space on a flat substrate; and two resistance temperature detectors (3, 5) are provided upstream and downstream of the heating resistor (4). The sides of the rectangular thermal insulating area which are parallel to the axis of air flow are longer than its sides which are perpendicular to the axis of air flow.
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