A water absorbent resin (water absorbing agent) and method for producing it are provided which improve, in a water absorbent article (in particular, a diaper) including a water absorbent resin as a water absorbing agent, the absolute absorption amount (g), liquid absorbing times (in particular, liquid absorbing times at the second instance and later), re-wet (g), and diffusion distance (%) of the water absorbent article.A particulate water absorbing agent of the present invention has a CRC, a proportion of particles with sizes of 600 μm to 150 μm as defined through a standard-sieve classification, an SST, and the value of the difference between an FST and the SST each within a predetermined range.