PURPOSE: To make it possible to perform small hole machining in any direction with control command from a robot device for improving controllability on an electric discharge machining device by making into an unit of a light weight electrode driving device having a turning means for a small hole machining electrode, and equipping the unit to a robot device for general purpose.

CONSTITUTION: An electrode driving device 22 equipped with an electrode 9, an electrode turning motor 32, an intake port 37a feeding machining liquid to a penetration hole in the center of the electrode 9 and a piezoelectric actuator 41 making the electrode 9 separate from a shorted part in a moment when short circuit between the electrode 9 and a work is generated at a time of machining, is equipped to a robot device for general purpose on an arm member 24. This device performs positioning on machining point and control action from start till finish on machining, namely drive on the motor 32, application of discharge voltage, press sending machining liquid, working feed and so on in accordance with command from a control unit on the robot device, and applies small hole machining in any direction to the work 6 on a fixed bed.