In an internal combustion engine provided with a variable valve operating apparatus which variably changes a valve operating characteristic of at least one of intake and exhaust valves, a reference intake pipe pressure and a reference fresh air ratio corresponding to a reference operating condition of the variable valve operating apparatus are computed based on the detection value of the engine operating condition, a fresh air ratio correction amount corresponding to an operating condition of the variable valve operating apparatus is computed based on the detection value of the intake pipe pressure and the reference intake pipe pressure, the reference fresh air ratio is corrected based on the computed fresh air ratio correction amount to compute a final fresh air ratio, and an operating amount of the control object in the internal combustion engine is computed based on the final fresh air ratio to operate the control object.

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