PURPOSE: To make the effective diameter of each nozzle properly adjustable displaying the optimum combustion property corresponding to the operational status of an engine by a method wherein a nozzle valve is inserted into a nozzle body slidably in the axial direction as well as freeturningly facing each other to make them turn facing each other.

CONSTITUTION: During low speed and load operation, the oil channel 14 of a nozzle valve 1 is communicated with the second nozzle 15b. Then the fuel pressurized by an injection pump is fed to an oil sump 11 through an inlet 9, an oil feeding channel 10 and when the valve 1 is lowered opposing to the tension of a spring 24, the oil channel 14 is communicated with the second nozzle 15b... to spray the fuel from the nozzle 15b... in the direction as shown by L1. On the other hand, when the engine is shifted to the operation under high load and revolution, the valve 1 is turned by a solenoid through a turning lever 8, a turning axle 7 to change the oil channel 14 to be communicated with the first nozzle 15a. Then when the valve 1 is lowered likewise, the fuel is sprayed from the nozzle 15a in the direction shown by L2.