Provided is a water-absorbing agent which is less likely to cause gel blocking and is suitable for a sanitary product and an absorbent article each being thin and containing a large amount of a water-absorbing agent, and which, while maintaining or hardly losing the other physical properties (a fluid retention capacity and a bulk specific gravity) of the water-absorbing agent, simultaneously achieves a high water absorbing speed (e.g., FSR), a high fluid retention capacity under load, high liquid permeability, and salt tolerance. The water-absorbing agent is a polyacrylic acid (salt)-based water-absorbing agent whose surface and its vicinity are crosslinked by an organic surface crosslinking agent, characterized by satisfying the following (A) - (D): (A) Free Swell Rate (FSR) of at least 0.28 g/g/s, or Absorption Time (Vortex) of 42 seconds or less； (B) Absorption Against Pressure (AAP) of at least 20 g/g； (C) Salt Tolerance Index represented by "Salt Tolerance Index = (CRCdw) / (CRCs)" where CRCdw is a centrifuge retention capacity (unit； g/g) for deionized water (dw), and CRCs is a centrifuge retention capacity (unit； g/g) for a 0.9 weight% saline, satisfying "Salt Tolerance Index ‰¤ 0.49 × CRCs - 7.47"； and (D) Bulk Specific Gravity of 0.55 to 0.70 g/cm 3 .
