An apparatus of the type in which the amount of fuel injected to an internal combustion engine is controlled by a control member arranged to be moved with a front wall urged forwardly by a return spring and rearwardly by negative pressure in a negative pressure chamber connected to an air intake passage of the internal combustion engine. A second negative pressure chamber is provided behind the foregoing negative pressure chamber and the foregoing return spring is supported by a second front wall, which is urged forward by a second return spring in the second negative pressure chamber, the interior of the second negative pressure chamber being selectively connected to the atmosphere and the air intake passage of the engine through a change-over valve.