PURPOSE: To vary the open-valve pressure freely with correspondence to the engine operating condition by providing means for moving a receiver of spring for energizing a nozzle needle in the direction to close an injection hole.

CONSTITUTION: Pressing force of spring 15 is controlled by fuel supply to a cylinder 27, and upon opening of solenoid valve 33 to feed pressurized fuel into the cylinder 27, the piston 26 is pushed to move to the left against a spring 29. Consequently, the control sleeve 19 engagable with piston 26 will rotate in the nozzle holder 12 to move the sleeve 19 downward and to push the spring receiver 18 thereby the spring 15 is compressed to increase the open-valve pressure for opening the injection port 10. While upon discharge of fuel from the cylinder 27, the piston 26 is pushed by the spring 29 to move to the right, and upon rotation of sleeve 19 in reverse direction by means of the piston 26, the sleeve 19 will move upward to extend the spring 15 thus to weaken the force of spring 15 for pushing the nozzle needle 13 and to lower the open-valve pressure. Consequently, the fuel injection rate can be controlled optimally.