PURPOSE: To prevent the damage in a driving system by controlling the output of an engine not to exceed the strength limit output of the driving system when the reduction ratio of a transmission is more than a prescribed ratio and further the rotating speed is withing a prescribed range.

CONSTITUTION: The position of the change lever 60 of a transmission 58 being connected to an engine D is detected by a shift position sensor 62, and together with the signal from a rotating speed sensor 56 this is input into a control circuit 100. On the end of a floating arm 32 being interlocked with the control rack 38 of a governor 1, the cam surface 42a of a stop cam 42 is abutted. The cam 42 is moved by a step motor 62 via a sliding table 44. When the reduction ratio of a transmission is more than a prescribed ratio and further the rotating speed is within a prescribed range, the step motor 52 is driven as much as the amount stored in a ROM 102 to move the stop cam 42 toward right. Thus, the engine output is restricted, and the damage in the driving system can be prevented.