PURPOSE: To prevent the injection timing from being affected by injection quantity and enhance controlling accuracy, by providing an auxiliary pump chamber, a unidirectional valve and an auxiliary discharging port.

CONSTITUTION: In a compression stroke, the rotation of a rotor results in that communication between the first and second inlet ports and the first and second supplying ports and communication between the auxiliary discharging port and a low pressure side passage are interrupted. On the contrary, communication between a distributing port and a discharging port and communication between a spill port and a low pressure side passage are made. Simultaneously with the compressing operation, a fuel in the second pump chamber opens the valve body of the unidirectional valve, and this pressure acts on a shuttle through the auxiliary pump chamber, whereby the shuttle is pushed rightward in the figure, thereby raising the pressure in the first pump chamber. When this pressure exceeds a predetermined value, a high-pressure fuel is injected into a combustion chamber of the engine through the distributing port which is in the communicated condition.