PURPOSE: To obtain a correct flow rate value even when two flow-rate values are handled due to disturbance in airflow in a bypass, by determining the intake air flow rate based on the output of a hot wire type flowmeter and the amount of control for the intake air flow rate.

CONSTITUTION: A control device 7 comprising a microcomputer is provided in a hot wire type flowmeter 6, which is provided in an intake air bypass 5. The output voltage US of the flowmeter 6 and the outputs of a rotary speed sensor, a throttle sensor (a) and a water temperature sensor (c) are inputted to the control device 7. When the output voltage US, the rotary speed N, the opening degree θ of the throttle, and the like are inputted, at first a flow rate Q is computed from the output voltage US. Then a factor KTRM, which corrects the flow rate Q based on the rotary speed N and the opening degree θ of the throttle, is computed. Thereafter the flow rate Q is multiplied by the factor KTRM, and the amount of correction is computed. Therefore the correct flow rate value can be obtained even when the flow rated Q have two values.