PURPOSE: To enable the machining of an accurate hole diameter, when a work is perforated while causing electrolytic etching on the surface of the work, by jetting an electrolytic solution containing a specific powder and an agent having a passivation effect to the work.

CONSTITUTION: Electrolytic etching is carried out by opposing an electrode 4 to a work 1 to be machined that has been set inside an electrolytic bath 3, and by feeding the electrolytic solution inside a reserving tank 6 to the end of the electrode 4 by a pump 61. In this case, as the electrolytic solution, that which is made of powder consisting of at least one kind of oxide, nitride, carbide, and boride having a mean grain diameter of 1μm or less, an agent having a passivation effect to the work, and an agent that dissolves into water for providing it with conductivity is used. Thereby, a passive film is formed on the surface of metal and the elution of metal is restained. On the other hand, the passive film on the bottom of the hole facing to the end of the electrode is removed by the fine powder, and the elution of metal is carried out only to this part.