To provide an airflow measuring device capable of assuring detection accuracy of the inhalation amount of air flowing through an intake pathway 2 by inhibiting pollution degradation or breakage of heat resistors (flow metering element), thermostatic resistive elements (temperature-compensating resistive element) and the like of a sensing section 4 of the airflow measuring device.

By preparing a sub-bypass channel 13 forming circulating rotational flow of air within a sensor body 3 of the airflow measuring device in addition to a bypass channel 12, the inhaled air flowing into the bypass channel 12 is made it more difficult to flow into the sub-bypass channel 13 from a communicating mouth 29. Thereby, dust contained in inhaling air flowing through the bypass channel 12 toughens to reach a sensing section 4 prepared within the sub-bypass channel 13. Therefore, as pollution degradation or breakage can be inhibited of heat resistors, thermostatic resistive elements and the like of the sensing section 4, detection accuracy can be assured of the inhalation amount of air at the heat resistors of the sensing section 4.