<；P>；PROBLEM TO BE SOLVED: To solve the problem of a gel obtained using the conventional water-absorbing resin incapable of always satisfying the long term stability under light (such as daylight) irradiation. <；P>；SOLUTION: A water-absorbing resin for a pet sheet (C) includes (A) a cross-linked polymer including (a1) a water-soluble vinyl monomer and/or (a2) a vinyl monomer, and (b) an internal cross-linking agent as the essential components. It satisfies the following requirements (1) and (2): (1) the total content of unpolymerized (a1), (a2) and (b) in the water-absorbing resin (C) being 10-200 ppm based on the weight of (C), and (2) the gel strength retention of a gel (G1) prepared by swelling the water-absorbing resin (C) with ion exchange water 50 times being 50% or more. A pet sheet using the water-absorbing resin for a pet sheet is also provided. <；P>；COPYRIGHT: (C)2011,JPO&INPIT
