The invention provides a marking method in which marking is performed on a protective film formed on a work with a high accuracy while suppressing a warpage and, also, a sheet for both protective film forming and dicing which is advantageously used in the method. The marking method comprises irradiating laser light to a laminated structure comprising a support film tensely supported by a ring frame, a protective film releasably laminated on the support film and a work fixed to the protective film, wherein the protective film is irradiated laser light from a side of the support film, to thereby mark the protective film.