PURPOSE: To eliminate the influence of the inertia of a DC motor, etc., almost by a method wherein a maximum duty corresponding to a set torque limit value is obtained even if an actuating lever is actuated with a maximum actuation stroke.

CONSTITUTION: A torque limit value setting means VR2, a maximum duty determining means MD, a duty setting means VR1 and an output control means are provided. A torque limit value is set by the torque limit value setting means VR2 and the maximum duty determining means MD determines a maximum duty corresponding to the set torque limit value. If an actuating lever is actuated, the duty setting means VR1 outputs a duty corresponding to the actuation stroke and, when the torque of a DC motor reaches the torque limit value, the DC motor is operated with a low speed by the output control means and the inertia of reduction gear mechanism is reduced. With this constitution, a work can be processed easily.