To improve fuel economy and an exhausting property by controlling fuel injection pressure and an injection speed.

In order to promote fuel pressurizing, a control valve is provided, which is actuated by a piezoelectric element via a hydraulic amplifier. In order to control the displacement amount of the hydraulic amplifier and to control a fuel injection amount by controlling the displacement amount of the control valve, the piezoelectric element is excited by a variable voltage source. The control valve has a configuration so as to give fuel injection in multiple stages, the low fuel injection pressure and the injection speed, and high fuel injection pressure and an injection speed succeeding thereto. The fuel injection in multiple stages can be achieved by controlling an exciting voltage level to the piezoelectric element. A pressure check valve is provided so as to lead fuel into a hydraulic amplifier chamber for excluding bubbles confined in the hydraulic amplifier chamber, to compensate fuel leakage from the chamber, and to make the fuel circulate through the chamber.