PURPOSE: To make a proper fuel supply attainble with a simple structure by installing a fuel injection nozzle whose effective area is variable, a fuel pressure regulator and a fuel flow regulator.

CONSTITUTION: Fuel in a fuel tank 7 is fed to a pressure regulating chamber 15 of a fuel pressure regulator 5 by a fuel pump 8 via a pressure regulating valve 17. Fuel in this pressure regulating chamber 15 is regulated to the specified positive pressure by the pressure regulating valve 17 and a pressure regulating spring 21 and sprayed out of a fuel injection nozzle 24, then it is mixed with intake air and fed to an engine. On the other hand, venturi negative pressure comes high with the increase of a suction air quantity, and intake manifold negative pressure comes low instead, so that, according to a pressure differential between a first vacuum chamber 29 and a second vacuum chamber 32, a fuel flow regulator 6 actuates a needle valve 33, making an effective area of the fuel injection nozzle 24 larger, and conversely making the effective area of the injection nozzle 24 smaller with the decrease of the suction air quantity. With this constitution, the fuel is properly feedable with a simple structure without receiving any influence of a tilt and an impact.