The invention provides a control device for judging whether
machining is possible. The control device (20) comprises a first ratio calculating unit (24) that calculates a maximum output value corresponding to the speed of a motor (11) , which is detected by a speed detecting unit (13) based on a
first relationship, and calculates a first ratio of an actual output in relative to the maximum output value; a second ratio calculating unit (25) that calculates a continuous nominal output value corresponding to the speed of the motor (11) , which is detected by the speed detecting unit (13) based on a second ratio , and calculates a second ratio of the actual power in respect to the continuous rated output value; and a judging unit (26) that uses the first ratio and the second ratio as a basis to judge whether at least one of an intermittent
machining and a continuous
machining of a workpiece is possible.