Provided is a method for analyzing, in the depth direction, a polymeric thin-film structure which comprises two or more polymer compounds, the method comprising labeling at least one of the polymer compounds with a stable isotope and repeating the step of subjecting the structure including the polymer compound labeled with a stable isotope to sputtering with sputtering ions along the depth direction thereof and the step of acquiring a mass spectrum of secondary ions including the stable isotope by means of time-of-flight secondary ion mass spectroscopy, thereby obtaining a depth profile of fragments including the stable isotope. Also provided is a method for analyzing an organic film in the depth direction, the method comprising forming an electroconductive carbon coating layer on the surface of the organic film and repeating the step of subjecting the carbon-coated organic film to sputtering with sputtering ions along the depth direction thereof and the step of acquiring a mass spectrum of secondary ions of
