PURPOSE: To simplify an engine body and to reduce cost by a method wherein a flow passage means to return a part of fuel fed with a pressure to an injection nozzle to a fuel tank comprises a return flow passage formed in a cylinder head body and communicated with an injection nozzle.

CONSTITUTION: An amount of oil fed from a feed pump to a fuel injection pump 13 is sufficiently higher than an injection amount and an amount of oil fed from the fuel injection pump 13 to an injection nozzle 3 is also higher than the injection amount. Surplus fuel is used for lubrication of a nozzle needle constituting the injection nozzle 3. Fuel after lubrication is recovered to a fuel tank 12 through a main flow passage 6 and a return line 10 by means of a branch passage 7. In this case, a return flow passage through which a part of fuel fed with a pressure through the injection nozzle 3 is returned to the fuel tank 12 is formed in a cylinder head body 2 by machining. This constitution prevents an influence from being exercised by the return flow passage during layout of other part and reduces the size of a device.