An air flow measuring device includes a housing, flow sensor, and a humidity sensor. The housing defines a bypass flow passage through which intake it passes. A part of intake air is taken into the bypass flow passage to pass through the bypass flow passage. The flow sensor includes a sensing part disposed in the bypass flow passage, and produces a signal which is in accordance with the flow rate of intake air as a result of heat transfer between intake air taken into the bypass flow passage and the sensing part. The humidity sensor includes a sensing part exposed to the intake passage, and projects from an outer wall of the housing into the intake passage. The humidity sensor produces a signal which is in accordance with humidity of intake ail flowing through the intake passage.