Experience shows that, in a material containing oxygen as a main component, an excess or deficiency of trace amounts of oxygen with respect to a stoichiometric composition, or the like affects properties of the material. An oxygen diffusion evaluation method of an oxide film stacked body includes the steps of: measuring a quantitative value of one of oxygen isotopes of a substrate including a first oxide film and a second oxide film which has an existence proportion of an oxygen isotope different from an existence proportion of an oxygen isotope in the first oxide film in a depth direction, by secondary ion mass spectrometry; and evaluating the one of the oxygen isotopes diffused from the first oxide film to the second oxide film.