An electric deionization device capable of sufficiently removing weak electrolyte components and producing processed desalting chamber having rectangular-parallelepiped frame 20, a compartment member 21 disposed in the frame 20 and, desirably, having conductivity, an ion exchange resin 23 filled in small chambes 22 formed by the compartment member 21, and an anion exchange membrane 24 and a cation exchange membrane 25 disposed so as to hold the frame 20. The compartment member 21 is formed in a hexagonal honeycomb shape. The ion exchange membrane 23 is the mixture of an anion exchange resin with a cation exchange resin, and its mixing ratio on the upstream side is different from that on the downstream side.