A method for producing a water-absorbent resin, characterized by adding a bisoxetane compound represented by the following general formula (1): wherein R is an alkyl group having 1 to 6 carbon atoms and n is an integer of from 0 to 6, to a water-absorbent resin precursor obtainable by polymerizing water-soluble ethylenically unsaturated monomers, and subjecting the components to a post-crosslinking reaction while heating and a water-absorbent resin obtainable by the method, characterized in that the water-absorbent resin has a retention capacity of physiological saline of 30 g/g or more, an absorption capacity of physiological saline under a load of 2.07 kPa of 15 ml/g or more, and a water-soluble substance of 20% by mass or less. The water-absorbent resin obtained by the method of the present invention is excellent in properties such as water-retention capacity, and water-absorption capacity under load, and also gives consideration to safety of the water-absorbent resin by reducing water-soluble substance. Therefore, the water-absorbent resin of the present invention can be preferably used, for example, in hygienic materials such as disposable diaper, incontinence pad and sanitary napkin, in particular, in disposable diaper.
