PURPOSE: To decrease a speed of opening a needle valve and to improve an injection cut of the valve, when it is closed, by providing a fuel introducing chamber, pressing the needle valve in a seating direction by a pressure of fuel from a fuel pressurizing chamber, in a fuel injection device and switching a condition between both the fuel pressurizing and introducing chambers to connection and disconnection conditions.

CONSTITUTION: Fuel in a fuel pressurizing chamber 33 is pressurized by a plunger 36 in a fuel injection device 1 and injected from an injection hole 444 via a fuel reservoir chamber 445 by opening a needle valve 446. A spring housing chamber 42a, containing a nozzle spring 46 pressing the needle valve, serves as a fuel introducing chamber and communicates with a fuel pressurizing chamber 33 by a communication path 6 through an electromagnetic opening and closing selector valve 5. The electromagnetic opening and closing selector valve 5 is energized closing after a start of pressurization and deenergized opening before a stop of pressurization, of fuel by the pump plunger 36. Accordingly, when the needle valve is opened, its opening speed is decreased by a damper effect of the fuel introducing chamber to prevent a sudden increase of temperature in ignition, and when the valve is closed, its closing speed is increased by the pressure to improve an injection cut.