PROBLEM TO BE SOLVED: To provide a water-absorbing material having excellent water- absorbing properties (water-absorbing magnification, water-absorbing rate, etc.), even in salt-containing solutions with high concentration such as sea water, a calcium chloride deliquescent aqueous solution, blood, body fluid (urine, sweet) or the like without deteriorating water-absorbing magnification and water- absorbing rate in purified water, in low ionic water or the like. SOLUTION: The water-absorbing material is characterized by obtaining it by reacting a polyacidic amino acid anhydride having at least one ethylenically unsaturated bond in the molecule (A) with a ethylenically unsaturated compound containing a sulfonic acid group and/or a ethylenically unsaturated compound containing a sulfonate group (B).
