To detect the amount of intake air with higher accuracy by accurately compensating a detection error of an air flow meter resulting from the pulsation of intake air even when a flow manipulating mechanism is mounted between a throttle valve and a combustion chamber for manipulating the flow rate of air therebetween.

When a swirl control valve and a variable valve timing mechanism are mounted as the flow manipulating mechanism, e.g., a pulsation/drift correcting coefficient K for compensating the detection error of the air flow meter resulting from the pulsation/drift of intake air in an intake passage is found in accordance with a throttle opening TA, an engine speed Ne, a swirl control valve opening VA and a cam angle θA. An air flow meter output GAH is computed after correcting an air flow meter output GA multiplied by the pulsation/drift correcting coefficient K and the amount of intake air into the engine combustion chamber is detected in accordance with the air flow meter output GAH after the correction.