As shown in the following Patent Literature 1, an excrement-treating material having a composite layer structure of a water-absorbable core part and a water-absorbable surface layer covering the surface of the core part and having enhanced water absorbability has been already known since before. The surface layer in the excrement-treating material of Patent Literature 1 is formed of a powder of a water-absorbing resin such as a water-absorbable polymer, and is formed by reacting the powder of a water-absorbing resin with a water content that is present on the surface of the core part to thereby bond the powder to the surface of the core part.
Furthermore, as shown in the following Patent Literatures 2 and 3, excrement-treating materials that are premised on the above-mentioned composite layer structure, which enable, upon absorption of excreted urine from a cat, a dog or the like, easy discrimination of a used part (a part that has received excreted urine) and a unused part (a part that has not received excreted urine) by the exposure of the color on the core part by permeation or immersion through the surface layer that has got wet, while ensuring a water-absorption ability, are already known. The surface layer in the excrement-treating materials of Patent Literatures 2 and 3 are each formed by using plant fibers as a major material and containing an adhesive such as starch and a water-absorbable polymer, and is formed by bonding to the surface of the core part through a water-soluble adhesive represented by polyvinyl alcohol (PVA).