A method for the preparation of a glucose polymer having an ion-exchanging ability comprises the steps of drying a mixed aqueous solution containing a raw glucose polymer and a polyvalent carboxylic acid to thus form a uniform powdery mixture and then subjecting the powdery mixture to a heat treatment. The method of the present invention can ensure the achievement of a high reaction efficiency, is economically advantageous since it never requires the use of any expensive catalyst and does not require the use of any complicated step for the removal of impurities. The glucose polymer prepared by the method of the present invention is biodegradable and can be used in, for instance, various foods and/or builders.
