To provide an internal combustion engine capable of improving anti-knocking performance of an engine while maintaining an output torque of the engine.

The internal combustion engine 1 has a port fuel injection valve 65 for injecting the fuel at an intake port 4, and a cylinder fuel injection valve 66 for injecting the fuel in a cylinder 2. In the internal combustion engine 1, an octane number of the fuel injected from the port fuel injection valve 65 is set to be higher than the octane number of the fuel injected from the cylinder fuel injection valve 66. When a volumetric efficiency is decreased in a high load operation of the engine, a fuel injection amount of the port fuel injection valve 65 is decreased and the octane number of the fuel injected from the cylinder fuel injection valve 66 is increased.