The changes in stress of anodic oxide film during anodic oxidation of the titanium electrode, which was prepared on a glass plate by a magnetron sputtering method, were measured quantitatively by a beam-bending method. The anodic oxidation of titanium was performed in pH 8.4 borate solution by a potential step from an open-circuit potential (0.33 V-RHE) to a certain potential. The compressive stress of ca. 0.5 GPa was generated in the anodic oxide film during anodic oxidation for 1 h in the potential range 1.7-10.7 V-RHE. Moreover. the compressive stress of the anodic oxide film due to electrostriction was measured by a cathodic potential sweep from the film formation potential to the flatband potential (0 V-RHE) Of the anodic oxide film, and its value was in good agreement with the calculated value. The compressive stress due to electrostriction was only 2-4% of the total compressive stress of the anodic oxide film. The Pilling-Bedworth ratio of the Ti/TiO2 film system supported the compressive stress of the anodic oxide film due to volume expansion of film formation. The transference number of oxygen ions in the film and the annihilation of ion vacancies were taken into consideration as factors influencing the compressive stress of the anodic oxide film.