PURPOSE: To dispense with a return guide for a pump plunger and to narrower a suction chamber in a fuel injection pump for an internal combustion engine.

CONSTITUTION: A rotation axial line of a pump cylinder 7 is arranged in a radius directional plane 8 of a rotational driven distributor 4. The distributor 4 is guided inside a cylinder liner 3 fitted inside a casing of a fuel injection pump, and a cam ring 18 surrounding the distributor 4 is arranged in the radius directional plane 8 including the rotation axial line of the pump cylinder 7. The cam ring 18 is provided with a cam face 17 directed to a pump plunger 6 protruded from the pump cylinder 7, and a roller shaft 15 is arranged between the cam face 17 and the pump plunger 6. As a fuel pressure inside a suction chamber 12 is always higher than a liquid pressure in a driving device chamber 2 during an operation of a fuel injection pump, the pump plunger 6 follows the cam face 17 according to a pressure difference between a the suction chamber and the driving device chamber.