To provide a device for measuring an engine intake air amount capable of improving accuracy of measuring an intake air amount by an air flow meter in an EGR control region.

The device measures the intake air amount of an engine 100 with an exhaust gas recirculation device 150 by the air flow meter 112 provided in an air intake passage 102. The device includes: an air amount ratio varying means for varying an air amount ratio to a flow passage 112C to a detection part 112D of the air flow meter 112 provided in the air intake passage 102; and a conversion expression changing arithmetic means for obtaining the intake air amount corresponding to an output voltage by changing a conversion expression between the output voltage of the air flow meter 112 and the intake air amount in response to variation in the air amount ratio by the air amount ratio varying means.