PURPOSE: To improve electrolytic polishing in efficiency by covering the cavity to be finished with an elastic substance and moving the abrasive-containing working fluid sealed in the cavity in order to allow the abrasive to remove the oxide film on the surface being finished.

CONSTITUTION: An object 2 to be worked is secured on a table 1. An elastic substance 4 is arranged so as to cover the cavity to be worked, and closely secured by a fixing member 6. The sealed cavity is filled with working fluid containing abrasive supplied from a working fluid regulating tank 1 by a pump 12 through a supply pipe 9 having a check valve 11 and a supply passage 7. Then a surface 5 is electrolytically polished by using a flexible electrode as a cathode and the object 2 as an anode. On doing this, the reciprocating motion of a pressure substance 19 causes the elastic substance 4 to be pressed downwards, and consequently the working fluid cyclically moves in the cavity. The movement permits the oxide film to be removed and exhausted through an exhaust passage 8.