PURPOSE: To cause good combustion under heavy load and improve starting under light load, by providing a fuel feed line with an auxiliary injection hole which is opened by moving a needle valve in the region of low pressure of fuel and with a main injection hole which is opened in the region of high pressure of the fuel.

CONSTITUTION: Under light load, fuel in the region of low pressure is introduced into a fuel chamber 8 so that only the main part 7 of a needle valve 4 is opened and the fuel in the chamber 8 is injected into a combustion chamber 1 through an auxiliary injection hole 13. At that time, no fuel film is made on the inside surface 14 of the combustion chamber 1 and a mixture is made in the central part of the chamber so that hydrocarbon and white smoke are prevented from being released and starting is improved. Under heavy load, fuel in the region of high pressure is introduced into the chamber 8 so that the needle valve 4 is much moved, the auxiliary part 11 of the valve 4 is opened and a large amount of fuel is injected through the main injection hole 10. At that time, the inside surface 14 of the combustion chamber 1 has a high temperature so that a fuel film is rapidly evaporated and burned.