PURPOSE: To provide a fuel injection device for diesel engine which can prevent abnormal rise of the engine speed while the engine remains off load through sensing of the condition with engine operating without load.

CONSTITUTION: The engine speed Ne is calculated by an Ne calculating means 31 on the basis of the output signal of an Ne sensor 19, and the rising rate ΔNe/Ne of the engine speed is calculated by a rise rate calculating means 35. A comparing means 36 compares the rise rate ΔNe/Ne with the specified value T, and if ΔNe/Ne is greater, actuators for stepping motors 3a-3d are moved to their specified positions with the aid of an actuator moving judgement means 34. The output signal of a clutch switch 23 is fed to a no-load judging means 38, and the same applies in case the clutch switch is put on.