A control apparatus stops supply of a fuel to an engine (a) when a value of a parameter relating to a misfire of the engine satisfies a misfire condition that is set based on an octane value of the fuel, or (b) when it is determined that a misfire may occur if an increased amount of the fuel is supplied to the engine in the case where ignition timing of the engine is retarded based on an octane value of the fuel, and the amount of the fuel is increased according to a retard amount of the ignition timing.