PURPOSE: To suppress decreasing an engine speed when applied a sudden load, by detecting a current value or an oil pressure value supplied to a load from a work machine, and supplying assist fuel to an intake route or a combustion chamber when an increasing factor of this detection value exceeds a prescribed value.

CONSTITUTION: In an engine work machine, a work machine 18 is connected to be associated with an engine 33, also to connect a fuel amount adjusting means 3 associated with a governing operating means 1 of the engine 33 through a governor mechanism 2. Here is detected a current value or an oil pressure value, supplied to a load 19 from the work machine 18, by a detecting means 20. On the other hand, a control means 6 is made in cooperation with the detecting means 20, also to make an assist fuel supply means 5 cooperate with the control means 6. When an increasing factor of the detected current value or oil pressure value is detected to exceed a prescribed value by the control means 6, the assist fuel supply means 5 is actuated by the control means 6. In this way, assist fuel is supplied only for a prescribed time to at least one of an intake route 4 or a combustion chamber.