PURPOSE: To obtain the titled polymer excellent in absorption of body fluid, by graft-polymerizing a water-soluble monomer in an aqueous solution containing xanthan gum and locust bean gum.

CONSTITUTION: A water-soluble monomer, e.g., (meth)acrylic acid, and, optionally, a compound having at least two vinyl groups in the molecule, e.g., methylenebisacrylamide, are added to an aqueous solution of xanthan gum and locust bean gum at a ratio of 4:6W6:4, and the graft polymerization is effected at a temperature ≤60°C in the presence of a ceric salt initiator. The polymerization system is heated to a temperature ≥60°C and then cooled by standing.

EFFECT: It is possible to obtain a highly absorptive polymer excellent in absorptivity in an ionic aqueous solution.

USE: Sanitary products, diapers, water-retainer, etc.