A retractable feeding rod is located in a guide cylinder. A workpiece retaining pipe is connected to a leading end of the guide cylinder which serves as a movable electrode and a feed-in passage for a workpiece positioned at an acute angle to the guide cylinder. It opens within the guide cylinder and a control surface is provided for appropriately regulating the advancing speed of the workpiece in an end or in the middle of a passage through which the workpiece is fed to the guide cylinder to prevent the guide cylinder from being damaged or worn by the workpiece that impacts the guide cylinder at a high speed.
