PURPOSE: To provide an air flow sensor preventing the degradation of detection accuracy due to the transmission of heat generated in a heat sensing resistor sensor for detection to a heat sensing resistor sensor for temperature compensation.

CONSTITUTION: A heat sensing resistor sensor 4 for detection and a heat sensing resistor sensor 5 for temperature compensation are inserted through a pair of holder holes 22a, 22b provided on a sensor holding stage 21 to position and fix at a constant distance and are projectively arranged in an air flow path 26 surrounded by a window frame 25. As the heat sensing resistor sensor 5 for temperature compensation is apart in a set distance from the heat sensing resistor sensor 4 for detection, the sensor 5 does not receive heat, so temperature compensation is exactly done and the detection accuracy of air flow sensor is improved.