The purpose of the present invention is to provide a novel topical adhesive skin patch by which the point in time to terminate application can be ascertained visually. In a topical adhesive skin patch provided with a support and a base material layer laminated to one or both sides of the support, or in a topical adhesive skin patch intended to be used by placing only a gel sheet against the skin surface, the base material layer or gel sheet includes an oil-in-water type gel base containing at least water, oil, an emulsifier, and a water-absorbent polymer, such that prior to application to the skin surface, the base material layer or gel sheet is opaque due to emulsification of the base material layer or gel sheet, and subsequent to application to the skin surface, moisture contained in the base material layer or gel sheet gradually evaporates causing the opacity of the base material layer or gel sheet to decline over time, so that decline in opacity over time can be visually ascertained.
