An electrodeionization apparatus is provided, in which enough electric current flows even when voltage applied between the electrodes is low, thereby sufficiently performing deionization. A single first cation exchange membrane, a single anion exchange membrane, a single second cation exchange membrane are arranged between a cathode and an anode so that a concentration-cathode compartment, a desalting compartment, a concentrating compartment, and an anode compartment are formed, in this order, between the cathode and the anode. The concentration-cathode compartment and the anode compartment are filled with a cation exchange resin, respectively. The desalting compartment is filled with a mixture of the cation exchange resin and an anion exchange resin. Fed into the anode compartment is raw water or deionized water. Water from the anode compartment is sent to the concentrating compartment and the concentration-cathode compartment sequentially.