An engine control apparatus controls a throttle valve opening degree in response to a demand output of a driver. A target charged intake air amount of air taken into a cylinder per intake stroke is set in response to the demand output. Based on an air pressure generated at an upstream side of a throttle valve, the maximum actual charged intake air amount is set as a maximum value of the actual charged intake air amount taken into the cylinder per intake stroke. The target charged intake air amount is normalized by calculating a ratio of the target charged intake air amount to the maximum actual intake air amount. The throttle valve opening degree is set based on the normalized target charged intake air amount and an engine speed. Then, a signal for actuating the throttle valve is output to a throttle actuator so that the throttle valve has the set opening degree. Fuel injection amount is set based on the target charged intake air amount.