Method for treating radioactive waste solution and treatment apparatus

Disclosed is a method for treating a radioactive waste solution containing a sodium salt. A radioactive waste solution containing at least one of sodium hydroxide, sodium hydrogencarbonate and sodium carbonate is fed to an anode chamber in an electrolytic cell provided with a positive electrode and a negative electrode respectively on both sides of a permeable membrane, which is selectively permeable to sodium ions, and the radioactive waste solution is electrodialyzed. In a cathode chamber, the sodium ions permeated through the permeable membrane are separated as sodium hydroxide from the radioactive waste solution. Radioactive substances, which have stayed in the anode chamber, are separated as a solution enriched with the radioactive substances, from the radioactive waste solution. Thesodium hydroxide and the solution enriched with the radioactive substances, which have been separated, are each recovered.