An engine control system includes pressure sensors (73, 74), position sensors (75, 76), pressure sensors (77, 78), a target revolution speed modification value computing unit (90), and a modification value adder (70r). A target revolution speed NR2 for use in control is computed based on changes of status variables such that the target revolution speed NR2 increases from the target revolution speed NR1 applied from an input unit (71), and then moderately returns to the target revolution speed NR1. In accordance with the computed target revolution speed NR2 for use in control, a target fuel injection amount FN1 is computed and a fuel injection amount is controlled. As a result, a drop of an engine revolution speed attributable to an abrupt increase of an engine load can be suppressed without sacrificing the work efficiency, and lowering of durability caused by an excessive increase of the engine revolution speed can be prevented.