PURPOSE: To enable an intake air quantity to be compensatingly controlled by the minimum number of sensors by correctively setting the intake air quantity based on a variation amount of charged intake air quantity inside a charging chamber between a compressor and a throttle valve estimated based on supercharging pressure.

CONSTITUTION: An intake air quantity of an internal combustion engine 2 is directly detected by an air flow meter upstream from a compressor 6. Supercharging pressure by an exhaust turbocharger 1 is directly detected by a supercharging pressure sensor 21 between an intercooler 19 and a throttle valve 12. A variation amount of a charging air quantity inside a supercharging chamber 22 between the compressor 6 and the throttle valve 12 is estimated based on the supercharging pressure detected the supercharging pressure sensor 21. The intake air quantity detected by an air flow meter 11 is correctively set based on the estimated result. Consequently, an intake air quantity detected error at the transient time particularly in the system provided with the intercooler 19 can be compensated with good response. The compensating control is performed by the minimum number of the sensors.