To provide a thermally transferable protective sheet which, upon forming a protective layer on a image-receiving member, can provide the protective layer without causing rainbow unevenness.A thermally transferable protective sheet which has a protective layer that comprises a peeling layer and an adhesive layer on at least one portion of one face of a substrate sheet, and is thermally transferable, and the peeling layer and the adhesive layer are respectively constituted by resins that have different upper and lower values of refractive indexes, with a refractive index of 1.5 serving as its border.