In a fuel injection pump having two kinds of plungers rotatably displaced by a common rack, each of one kind of plungers ceasing fuel supply and each of the other kind of plungers supplying fuel during idling of an engine, a measuring screw-like groove of each plunger ceasing fuel supply during idling of the engine has a longitudinal groove communicating with a plunger pump chamber. The longitudinal groove is of relatively enlarged width, and a cut portion crossing at a right angle to said longitudinal groove is provided at the intersection of the longitudinal groove and the upper edge of the screw-like groove. The depth of this cut portion increases toward the longitudinal groove.