PURPOSE: To heighten separation efficiency between monosaccharides and disaccharides by preparing an anion-exchanger from a copolymer of a vinyl alcohol unit having specified hydroxy group and anion-exchangeable group each and a crosslinkable monomer.

CONSTITUTION: A part of ester groups of a copolymer prepared by copolymerization of vinyl carboxylate and a crosslinkable monomer is saponified or ester interchanged. Then, after a part of hydroxy groups is reacted with halogenocarboxylic acid halide, epichlorohydrin, etc., the resultant copolymer is reacted with ammonia or various amines to give an anion-exchanger. The anion-exchanger has 0.5-4.0meq/g of hydroxy derived from vinyl alcohol unit, 0.02-5.0meq/g anion-exchange capacity, 0.5-4.0g/g of water retaining capacity, and crosslinking monomer ratio X; 0.45≤X≤0.8.