[en] Purpose: To reduce the quantity of radioactive waste produced by decontamination without decreasing the decontaminating effect due to the conventional electrolytic polishing method. Method: An electrolytic tank is filled with electrolyte of aqueous sodium chloride solution, metal treating material adhered with radioactice metal oxide and pair electrodes are dipped in the solution, and a current is flowed with the metal treating material as an anode. Part of the electrolyte is continuously removed by pump, and the sludge containing contaminated material and metal treating material hydroxide are isolated via a filter. After heavy metal ions are selectively adsorbed to an oxine added active charcoal. The filtrate is fed to the active charcoal, and is then returned to the tank to be reused. (Seki, T.)