PURPOSE: To permit to reduce the height of the fuel injection device by a method wherein a return spring is arranged between the outer periphery of side surface of a tappet and a housing in the fuel injection device for a Diesel engine or the like.

CONSTITUTION: A return spring 2 is arranged between the outer periphery 16 of the seat of the tappet 1 and a housing 4 while a tappet roller 10 is abutted against a cam. According to this constitution, the tapper 1 moves up-and-down under utilizing a pin 17 and a longitudinal groove 24 for guiding, a plunger 7 cooperates to move up-and-down, fuel flows into a plunger chamber 8 upon the descending of the plunger 7, the fuel is pressurized upon the ascending of the plunger and the fuel is injected when the pressure has arrived at the opening pressure of a delivery valve 11. Thus, a distance between the upper surface of the tappet and the housing may be shortened to the stroke amount of the tappet and, therefore, the height of the fuel injection device may be reduced.