Ytterbium-doped SrZrO3 has been studied by thermogravimetric analysis (TGA), differential thermal analysis (DTA), powder X-ray diffraction (XRD), and XAFS spectroscopy. A broad endothermic peak was observed in the DTA curve for 5 mol% Yb-doped SrZrO3 at 812 degrees C, accompanied with a small weight loss, which is considered due to a mass loss of oxygen. The weight recovered its value in the cooling process at the lower temperature of 740 degrees C. The weight loss and gain in the heating and cooling process, respectively, shows a hysteresis loop. There exist at least 2.3 atom% oxide ion vacancies at high temperature. The two lattice constants become the same value above about 800 degrees C, indicating a phase transition for 5 mol% Yb-doped SrZrO3, which is consistent with the results from TGA and DTA. The oxide ion vacancies produced by substitution of tetravalent zirconium ions by trivalent ytterbium ions ate localized not near zirconium ions, but near ytterbium ions.