Abstract: The EGR gas flow is established based on the difference between an assumed value and a control target value of non-air components partial pressure calculated from target control values such as engine torque and at the same time the intake air flow passing through a throttle valve is established based on the difference between an assumed value and a control target value of air components partial pressure and based on the air components within EGR gas. Further, based on thus established EGR gas flow and the intake manifold pressure, the operating amount of an EGR actuator is calculated and based on thus established air flow passing through the throttle valve, the operating amount of an throttle actuator is obtained. Further, based on an estimated value of air components partial pressure, a final basic fuel injection amount is determined.