Common rail fuel injection apparatus and control method thereof

A common rail fuel injection apparatus includes a pressure-increasing piston (3) for increasing the injection pressure, and a control chamber (4) for controlling the position of the pressure-increasing piston (3) so as to control the injection pressure. An input constricted portion (5) for setting an amount of flow of the fuel that enters the control chamber (4), and an output constricted portion (6) for setting an amount of flow of the fuel that exits the control chamber (4) are formed. The input constricted portion (5) is connected to a common rail (2) via a pressure increase control valve (7). By opening and closing the pressure increase control valve (7), the injection pressure of fuel injected from an injector (1) is changed. Therefore, the injection pressure of fuel injected from the injector (1) can be changed as requested without a need to process component parts with high precision.