PURPOSE: To obtain a highly water-absorbing resin which suffers little from the deposition of polymer scales on the inside wall, etc., of a reactor during its production, is suppressed in the formation of fine particles, has an easily handleable suitable mean particle diameter, a sharp particle diameter distribution, a high strength of a swollen gel, and a high water-absorbing capacity, and is reduced in the extent of oozing of the absorbed substance.

CONSTITUTION: An aqueous solution of a water-soluble unsaturated monomer comprising a partially neutralized salt of (meth)acrylic acid is subjected to a reverse-phase suspension polymerization reaction in the presence of a β-1,3- glucan in a hydrocarbon solvent to obtain a highly water-absorbing resin. After the water content of this resin is adjusted to 10-30wt.%, the resin is brought into contact with a surface crosslinking agent to initiate the crosslinking reaction of the surface of the resin and 5-20wt.% water is added to the system when 20-85wt.% of the entire crosslinking agent has reacted with the resin to continue the crosslinking reaction.