Fuel injection device of an engine

A fuel injection device provided with a fuel injector for injecting fuel to be fed into a combustion chamber of an internal combustion engine and a reservoir for temporarily storing fuel fed to the fuel injector, where fuel is injected at least two times in one engine cycle of the internal combustion engine, pulsation of fuel occurring in the fuel injector due to a prior injection comprised of a first fuel injection is transmitted to the reservoir, reflected at the reservoir, and returns to the fuel injector and, due to the effect of the returned pulsation, the fuel injection amount at a later injection comprised of a second fuel injection fluctuates, the fuel injection device of an internal combustion engine employing as parameters affecting the fuel injection amount at the later injection an opening timing of the fuel injector and an injection pressure of fuel from the fuel injector, estimating the amounts of fluctuation of the parameters at the later injection arising due to the pulsation, and controlling a control value relating to operation of the fuel injector based on the estimated amounts of fluctuation of the parameters at the later injection so that the target amount of fuel is injected from the fuel injector at the later injection.