As characteristics that are not known at all, and control of particulate water-absorbing agent "under pressure flow-through efficiency (PPUP)" and, further, to control at the same time "granularity" and "colored" further. The present invention is a particulate water-absorbing agent satisfies the following (a) ~ a (c). (A) flow-through pressure efficiency (PPUP) is 50-100%. (YI) and is 0~10, (b) the degree of yellow, yellow rate of change of the 14-day coloring promotion test after a relative humidity 70 ± 1 ℃, 95 ± 1% (ΔYI) is 100-150%. 0 to 5% by weight, as defined in (c) standard sieve classification, particles of less than 150μm, mass-average particle diameter (D50) is from 0.20 to 0 logarithmic standard deviation of the particle size distribution and 200~550μm, is (σζ) is .40.従来全く知られていない特性として、粒子状吸水剤の「加圧下通液効率(PPUP)」を制御し、さらに、さらに「粒度」および「着色」を同時に制御する。本発明は、下記(a)~(c)を満たす粒子状吸水剤である。(a)加圧下通液効率(PPUP)が50~100%である。(b)黄色度(YI)が0~10、かつ、70±1℃、95±1%相対湿度下で14日間着色促進試験後の黄色度変化率(ΔYI)が100~150%である。(c)標準篩分級で規定される、150μm未満の粒子が0~5質量%、質量平均粒子径(D50)が200~550μm、かつ粒度分布の対数標準偏差(σζ)が0.20~0.40である。
