PURPOSE: To obtain the titled fibers, capable of losing the strength in a water absorption state, readily disposable and useful as sanitary products, by spinning an aqueous solution containing a polycarboxylic acid having a specific content of carboxyl groups and weight-average polymerization degree and polyhydric alcohol in a high concentration and heat-treating the resultant fibers.

CONSTITUTION: An aqueous solution containing a polycarboxylic acid, e.g. polyacrylic acid, etc., having at least 7 mequiv./g carboxyl groups and containing 25W90% thereof in the form of an alkali metal salt and/or monovalent amine salt and 1,000W30,000 average polymerization degree and a polyhydric alcohol, e.g. glycerol, etc., in an amount of 0.1W10wt% based on the carboxylic acid as components in a concentration as high as ≥35wt% as a spinning solution is spun by a dry spinning method while applying at least 2 times draft and the resultant fibers are heat-treated to afford the aimed highly water absorbing fibers.