An object of the present invention is to provide a water absorbing agent having a low amount of
residual monomer, small variance of the amount of
residual monomer among ranges of
particle size distribution and favorable absorption properties, and being sanitary; an absorbing article; and a method for the production of a water absorbing agent. The water absorbing agent of the present invention has the amount of
residual monomer of not higher than 500 ppm, and a residual
monomer index of not greater than 0.30. The method for the production includes a first step of obtaining a hydrogel
polymer by polymerizing an
aqueous solution of a
monomer including an unsaturated
carboxylic acid and / or a salt thereof in the presence of a crosslinking agent; a second step of obtaining a water absorbent resin precursor which is in
powder form and includes particles having a particle size of 300 to 850 μm and particles having a particle size of smaller than 300 μm as main components by
drying said hydrogel
polymer followed by pulverization and classification to adjust the
particle size distribution, a third step of obtaining a water absorbent resin by heating a mixture of said water absorbent resin precursor and a surface crosslinking agent, which can form an
ester bond around the surface of said water absorbent resin precursor, a fourth step of adding by spraying an
aqueous solution that includes a
sulfur-containing
reducing agent to said water absorbent resin, and a fifth step of subjecting the mixture of the water absorbent resin and said
aqueous solution to a heat treatment under an
airflow of not lower than 40° C. but not higher than 120° C.