PURPOSE: To enable the aspiration of additional fuel of a sufficient flow quantity in a high-load operation region of an supercharger-equipped engine by constituting the device in such a way that an additional fuel measured by a power valve is aspirated into a venturi through a power nozzle other than a main nozzle.

CONSTITUTION: When a power valve 11 is opened in a high-load operation region in which the negative pressure in an intake pipe is low, an additional fuel measured by a valve port 14 is aspirated into the intake passage 2 through an additional fuel passage 26 due to the venturi negative pressure acting on a power nozzle 25. When the engine enters a high-load high-speed operation and the negative pressure in the intake pipe becomes relatively high, a diaphragm 21 displaces towards a negative- pressure chamber 22 to decrease the opening of the power valve 11, however, since the venturi negative pressure is also increased, the amount of aspiration to the intake passage 2 is not decreased. On the other hand, at the time of high-load low-speed operation, since the negative pressure in the intake pipe is extremely low, the opening of the power valve 11 is increased, however, since the venturi negative pressure is very low, the amount of aspiration to the intake passage 2 is not increased. Thus, the amount of additional fuel can be optimized, and fuel economy can be enhanced.