To provide an intake air control device for an internal combustion engine capable of simply ensuring a detection accuracy of the amount of intake air at the occurrence of a reverse flow at low cost.

ECU 40 reads a detection value outputted from an air flow sensor 26 and judges whether or not the reverse flow is generated based on the read detection value, i.e., the amount of intake air detected by an air flow sensor 26. Then, when the ECU 40 judges that the reverse flow is generated, it outputs a control signal to an electric throttle so as to make an opening of a throttle valve 29 small. Thereby, the electric throttle 28 acts to throttle the throttle valve 29.