With respect to water-absorbent resins, there are provided a method of manufacturing a water-absorbent resin having an appropriate BET specific surface and a water-absorption rate and a water-absorbing agent and an absorbent article that are formed by using the water-absorbent resin. In a first aspect of the present invention, when reverse phase suspension polymerization of two steps or more is performed on a water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium in the presence of at least an azo compound, a peroxide and an internal-crosslinking agent, the used amount of the internal-crosslinking agent at the time of the polymerization of a first step is adjusted to fall within a range of 0.015 to 0.150 mmol per mole of the water-soluble ethylenically unsaturated monomer used at the time of the polymerization of the first step and the polymerization is performed such that the BET specific surface area of secondary particles formed by agglomeration of primary particles obtained is controlled.