PURPOSE: To eliminate the uselessness of an electrode and eliminate the error of a worked shape and improve reliability by oppositely arranging a thin hole guide to a workpiece and installing an insulating grease guide for suppressing the electrode vibration between a revolving device and the thin hole guide.

CONSTITUTION: A thin wire electrode 1 is installed onto a revolving device 5 installed onto a chuck 4, and is revolved, and then lowered, and the top edge is inserted into a grease guide 7 and a thin hole guide 2, and allowed to reach a workpiece 3, and working is carried out. Then, the top edge and the outer peripheral part of the thin wire electrode 1 are applied with grease as lubricating agent by a grase guide 7, and the thin wire electrode 1 is smoothly inserted into the thin hole guide 2, too. Further, since the grease of the grease guide 7 is not a fixed guide but a soft guide for the movement of the thin wire electrode 1, the vibration, deformation bending, etc. during the revolution of the thin wire electrode 1 can be suppressed. Therefore, the uselessness of the thin wire electrode 1 can be eliminated, and the error in the working shape can be suppressed, and high reliability can be obtained.