An object of the present invention is to provide a disposable diaper having a reduced amount of return and an excellent liquid uptake rate regardless of the concentration and configuration of the water-absorbing agent in the absorbent body. SOLUTION: The water-containing gel-like crosslinked polymer obtained in the polymerization step is pulverized to a specific weight average particle size while being adjusted to a specific range while adjusting the absorption capacity and surface tension of the water-absorbing agent. A water absorbing agent excellent in GCA (Gel Capillary Absorption) and FGBP (Free Gel Bed Permeability) is obtained by adding a liquid permeation improver during or after surface cross-linking.【課題】吸収体中の吸水剤濃度や構成によらず、戻り量が低減され、優れた液の取り込み速度を持った紙おむつを提供することである。【解決手段】吸水剤の吸収倍率、表面張力を特定の範囲に調整しつつ、重合工程で得られた含水ゲル状架橋重合体を特定の重量平均粒子径まで粉砕し、乾燥した後、表面架橋中又は表面架橋後に通液向上剤を添加することによって、ＧＣＡ（Ｇｅｌ Ｃａｐｉｌｌａｒｙ Ａｂｓｏｒｐｔｉｏｎ）とＦＧＢＰ（Ｆｒｅｅ Ｇｅｌ Ｂｅｄ Ｐｅｒｍｅａｂｉｌｔｙ）に優れた吸水剤を得る【選択図】図１
