To provide a method and an apparatus for supplying fuel of an internal combustion engine which can realize a proper burning state coincident with the operating state of the internal combustion engine.

The method for supplying the fuel of the internal combustion engine includes the steps of bringing the fuel into contact with a catalyst in a supercritical state or a subcritical state, and spraying the obtained modified fuel in a combustion chamber. The apparatus for supplying the fuel of the internal combustion engine includes a fuel tank, the combustion chamber, and a fuel spraying means for spraying the fuel in this combustion chamber. The apparatus also includes a supercritical generating means for making the fuel from the fuel tank the supercritical state or the subcritical state, and the catalyst containing a catalytic component for modifying the fuel of the supercritical state or the subcritical state generated by this supercritical generating means. Such a supercritical generating means is disposed between the fuel tank and the fuel spraying means. Such a catalyst is disposed between the supercritical generating means and the combustion chamber, etc.