PURPOSE: To perform highly accurate finish work at the leading edge of a choked hole, by performing electrolytic abrasive grain polishing while pressure contacting a tool wound with a resilient member for supporting abrasive grains at the tip of a rotary support and rotating.

CONSTITUTION: Liquid-pass resilient member supporting abrasive grains is wound and fixed at the leading edge 7 of a conductive rotary support 2 having conical shape similar with the leading edge section of a choked hole 3 to provide a tool. Then said tool is pressure contacted against the leading edge 5 of said hole and rotated while feeding electrolyte to apply voltage thus to perform complex work of electro-chemical machining and grain polishing. NaNO3, KNO3, etc. where passive state film are easily formed are preferable as said electrolyte.