An apparatus for controlling an internal combustion engine has an amount-of-intake-air control unit for generating a command value for the opening of a flow control valve in an intake passage of the engine, which emits exhaust gases through a catalytic converter, so as to increase an amount of intake air introduced into a combustion chamber by a predetermined quantity greater when the engine operates in an idling mode after it has started to operate than when the engine operates in a normal idling mode, and controlling the opening of the flow control valve based on the generated command value, and an ignition timing control unit for controlling the ignition timing according to a feedback control process to correct the ignition timing so as to be retarded in order to converge the rotational speed of the engine to a predetermined target rotational speed while the amount of intake air is being increased. The amount-of-intake-air control unit successively acquires amount-of-heat data representing the amount of heat energy actually given to the catalytic converter by exhaust gases flowing into said catalytic converter while the amount of intake air is being increased, and corrects the command value for the opening of said flow control valve according to a feedback control process in order to converge the acquired amount-of-heat data to a predetermined target value representing an amount of heat energy to be given to said catalytic converter.