An ion exchanger includes a sheet-shaped positive ion exchanger 2 in which binder particles 5 and positive ionic exchange resin particles 4 are mixed with each other, and a sheet-shaped porous negative ion exchanger 3 in which binder particles 7 and negative ionic exchange resin particles 6 are mixed with each other, the positive ion exchanger 2 and the negative ion exchanger 3 are bonded to each other to form an interface, and capacity of the negative ion exchanger 3 is greater than that of the positive ion exchanger 2. Therefore, the porous ion exchanger 1 is formed and absorbing ability of ion is increased, capacity of the negative ion exchanger 3 is made greater than that of the positive ion exchanger 2, regenerating ability of the ion exchanger with respect to absorbing ability of ion can be secured, and ion absorption and regeneration processing is carried out efficiently.