PURPOSE: To prevent oil film breakage by forming a cylindrical recession in a shoe, which gives a fuel press-transferring plunger the operating force, and fitting therein a sub-plunger, which is integrated into one body together with the plunger, in a freely slidable manner, thereby forming a sufficiently strong lubricating oil film between the shoe and a roller.

CONSTITUTION: As a rotor 2 rotates, an injection pump receives the operating force via both a roller 5 and a shoe 4, sucks the fuel into the central part of the rotor 5 by means of a plunger 3, which makes reciprocal movement in the direction of the rotor diameter, and discharges the fuel toward a distributing port. In this case, a cylindrical recession 41 is provided in the shoe 4, and a sub-plunger 6 having a small diameter, which is fitted into the recession 41 form a pressure chamber P, which is opened at a roller receiving surface 4a of the shoe 4 via a high pressure passage 42. In addition, the pressure chamber P is connected to the outside through a low pressure passage 61 provided with a check valve, which is closed when the internal pressure of the chamber P goes up. Meanwhile, the sub-plunger 6 is energized to the outside by a coil spring 7.