A particulate water absorbing agent of the present invention includes a water absorbent resin, having a cross-linking structure, whose surface has been cross-linked by adding a surface treatment agent, wherein: (i) a mass average particle diameter (D50) ranges from 200 to 600 µm and 95 to 100 wt % of a particulate water absorbing agent whose particle diameter ranges from less than 850 µm to not less than 150 µm is contained with respect to 100 wt % of whole the particulate water absorbing agent, and (ii) a logarithmic standard deviation (σζ) of particle size distribution ranges from 0.25 to 0.45, and (iii) a compressibility rate defined by a following equation ranges from 0 to 18 %, and (iv) a surface tension of a supernatant liquid obtained in 4 minutes after dispersing 0.5 g of the particulate water absorbing agent in 50 ml of physiological saline whose temperature is 20°C is 55 mN/m or more, the compressibility rate %=P−A/P×100 where P represents a tapped bulk density of the particulate water absorbing agent and A represents a loose bulk density of the particulate water absorbing agent.
