The present invention relates to a water-soluble polymer composition which comprises a water-soluble poly(meth)acrylic polymer and a gelation rate retarding agent, and a composition for forming a plaster layer of a skin patch which is obtainable by adding a polyvalent metal compound to the water-soluble polymer composition. When a polyvalent metal compound is added, the aforesaid water-soluble polymer composition shows an appropriate induction period before the start of the hardening of the gel. When the water-soluble polymer composition is used for forming a plaster layer of a skin patch, therefore, additive ingredients can be uniformly mixed and the procedure for coating to a support can be facilitated.
