An electrodelonization apparatus comprising multiple anion exchange membranes 13 and cation exchange membranes 14 that are alternately arranged between a cathode 12 and an anode 11 to alternately form concentrating compartments 15 and desalting compartments 16 is described. The concentrating compartments 15 and the desalting compartments 16 are filled with ion exchangers, and the filling ratio of anion exchanger to cation exchanger of the ion exchanger in the concentrating compartments 15 is higher than that of the ion exchanger in the desalting compartments 16.