PURPOSE: To prevent an increase of a tuppet side pressure angle when an injection pressure reaches the maximum for a fuel injection pump in which a plunger is driven by a fuel injection cam through a roller tuppet by offsetting a fuel injection cam axial center to a tuppet roller axial center.

CONSTITUTION: A plunger 2 is reciprocated through a tuppet roller 5 by rotation of a fuel injection cam shaft 6 interlocked with action of an engine of a diesel engine, so fuel sucked from a fuel passage into a high pressure chamber is boosted when the plunger 2 moves up to push and open a discharge valve 14 to be discharged to be supplied to a fuel injection nozzle. In this case, a fuel injection cam axial center 0 is disposed to be offset toward right to a tuppet roller axial center O1 for a predetermined quantity when the cam shaft 6 rotates clockwise, and toward left when it rotates counterclockwise. An increase of a tuppet side pressure angle is thus prevented when an injection pressure reaches the maximum so as to prevent fatigue breakage and avoid reduction of output heat efficiency.