An HC supplementing device mounted in an exhaust purification device of an internal combustion engine wherein, in order to simply increase the amount of HC to the exhaust purification device corresponding to the operating condition of the engine, attention is paid to the fact that the feed pump which pressurizes the fuel to a relatively low pressure and supplies the same to the fuel injection pump generates a feed pressure of a magnitude which changes in accordance with the operating conditions of the engine, for example, the engine speed, one part of the fuel of that feed pressure is taken out and supplied to the exhaust purification device assists the exhaust purification action as the increased HC.