An electronically-controlled cylinder fuel supply system in which an injector and an ignition plug are provided for each of combustion chambers, in which on the basis of an instruction signal to an engine and a speed of revolution of the engine, the fuel injection initiation timing and valve open duration of the injector, the ignition timing of the ignition plug and the quantity of suction air are determined through retrieval of values from a map stored in a ROM, in which a throttle valve is controlled such that the suction air quantity measured by an air flow meter coincides with the suction air quantity determined by the map retrieval, and in which the injector is provided with a fuel holding portion for temporarily holding the fuel injected during the lowered pressure of the combustion chamber and a vibration element for vibrating the fuel holding portion to atomize the fuel to thereby scatter the atomized fuel into the combustion chamber.