A knocking determining apparatus of an internal combustion engine that includes an in-cylinder injector and an intake port injector and that determines knocking based on an output signal of a knock sensor. The knocking determining apparatus includes a knocking determination prohibition unit prohibiting, when a ratio of fuel injection from the in-cylinder injector and the intake port injector is changed, knocking determination for a prescribed period after that change, or a knocking determination level change unit changing a knocking determination level for a prescribed period after that change.