PURPOSE: To improve operation efficiency and machining accuracy for boring by providing a guide mechanism which seizes a minute wire electrode cut between a cutting mechanism and the arm of the minute wire electrode supply side of a supporting frame to guide the cut end of the minute wire electrode to the prepared hole of a bored material.

CONSTITUTION: A work mechanism 2 is operated to locate the next prepared hole of a bored material P right under a minute wire electrode T, and a guide mechanism 8 is operated to lower the cutting end of the minute wire electrode T. The minute wire electrode T is inserted into the prepared hole of the bored material P and the insulator of the arm 32 of the supporting frame 3 to be connected to the fluid cyclone 91 and the bringing roller 92 of a recovery mechanism 9. Under this condition, after the guide mechanism 8 is moved upward for standby high voltage is applied to the minute wire electrode T from an electric source supply mechanism 5 so that the minute bore-finishing of the prepared hole of the bored material P may be carried out by discharging machining using high voltage energy.