An engine control apparatus comprised of an engine control ECU has a program preloaded therein for determining a combustion rate (actual combustion rate) corresponding to the ratio of an ideal heat generation quantity (target heat generation quantity) estimated to be generated from a fuel supply quantity, and an actual heat generation quantity actually generated by the fuel supply quantity. The engine control apparatus controls pilot injection timing with a controlled variable corresponding to the thus determined combustion rate so as to increase the combustion rate.