Provided are: a water-absorbing resin which, when used as an absorbent, retains a high water-absorbing ability and has such a property that the liquid to be absorbed is highly diffusible therethrough and can be inhibited from oozing out backward； and an absorbent article formed using an absorbent including the water-absorbing resin. The water-absorbing resin according to the present invention is a water-absorbing resin obtained by polymerizing a water-soluble ethylenic monomer in the presence of an internal crosslinking agent and thereafter crosslinking the polymer with a post-crosslinking agent, characterized in that when subjected to a liquid flow test, the water-absorbing resin has an effective absorbent index (K) indicated by equation (I) of 250 or greater. Effective absorbent index (K) = [(liquid flow amount) (g)] * [(artificial-urine absorption ratio) (g/g)] (I).本發明提供一種吸水性樹脂及吸收性物品，該吸水性樹脂使用於吸收體時，能夠一邊維持高吸水能力一邊具有對被吸收液的高擴散性，而能夠使回流量降低，該吸收性物品使用了包含該吸收性樹脂之吸收體。本發明的吸水性樹脂，其是藉由使水溶性乙烯性不飽和單體在內部交聯劑的存在下進行聚合，並且利用後交聯劑進行後交聯來獲得，其中，該吸水性樹脂的特徵在於：當使用該吸水性樹脂來實行下述的液流試驗時，以公式(I)所表示的吸收體有效指數K是250以上，吸收體有效指數K=液流量(g)×人工尿吸收倍率(g/g)…(I)。
