Disclosed is an engine fuel supply apparatus which can be made smaller in size and in which the amount of fuel in an air-fuel mixture can be increased with a fast response in correspondence with the operation of a throttle valve when the engine is accelerated rapidly. The fuel supply apparatus is provided with a fuel booster pump. A portion of an air-fuel mixture is introduced into a negative-pressure chamber of the fuel booster pump via a negative-pressure chamber channel, and the fuel booster pump is actuated. The actuation forces air in a pump chamber to flow into a pressure chamber, and fuel in a fuel storage chamber is temporarily supplied to a carburetor.