To easily shape the rate by providing a control valve member to be driven by a solenoid, and providing an amplifier piston to be driven by the fluid pressure through the control valve member to inject the pressurized fuel from a nozzle port by the piston.

A control valve member 18 is mounted in a cavity 14 of an injector body 1 provided with a solenoid 12, and the control valve member is urged to the side to close a high pressure working fluid inlet 15 by a compression spring 19. In this condition, the cavity 14 is opened for the low pressure working fluid drain 16. The solenoid 12 is excited and the control valve member 18 is lifted against the compression spring 19, and when the high pressure working fluid inlet 15 is opened, a piston 35 is advanced in a piston bore 17 against a compression spring 60, a needle check 30 is pressed by the pressurized fuel against a return spring 32, and the fuel is ejected from a nozzle port 25 to be released.