Fuel injection quantity control device

A fuel injection quantity control device for controlling an actual revolution speed En of an engine to a target revolution speed Eo, comprises difference computation unit (1) for subtracting the actual revolution speed En from the target revolution speed Eo and finding the difference e therebetween; proportional term computation unit (2) for multiplying the aforesaid difference e by the prescribed proportionality constant Kp and finding a proportional term output value Qp; integral term computation means (3) for finding an integral term output value Qi which is obtained by integrating the product of the aforesaid difference e and the prescribed integration constant Ki; differential term computation unit (5) for finding a differential term output value Qd which is obtained by multiplying the value obtained by differentiating the aforesaid difference e by the prescribed differentiation constant Kd; and injection quantity computation unit (6) for adding up the proportional term output value Qp and the integral term output value Qi and determining the injection quantity.