A control apparatus for an internal combustion engine is applied to vehicles equipped with a so-called drive by wire. When one of several control systems within the control apparatus fails, the drive is urged to obtain repairs. Also, even when all of the several control systems of the drive by wire fail and the failures of these control systems cannot be detected, unpredictable motion of the throttle valve can be prevented, thereby enhancing vehicle safety. The present invention includes a plurality of electronic throttle control systems for electrically driving a throttle valve of an internal combustion engine, a failure detecting mechanism for detecting failures of the electronic throttle control systems, intake air volume control mechanism for driving the throttle valve in a closing direction and also supplying a predetermined intake air volume to the internal combustion engine if it is judged that all electronic throttle control systems have failed, and output suppression mechanism for controlling the driving of the throttle valve by a normal electronic throttle control system and also suppressing output of the internal combustion engine corresponding to the operational quantity of the accelerator pedal if the failure determining mechanism determines that one electronic throttle control system among the several electronic throttle control systems has failed.