The state of platinum in the zirconium oxide promoted by platinum and sulfate ions (Pt/SO42--ZrO2) has been investigated by means of Pt L-edge XAFS (X-ray absorption near edge structure (XANES)/extended X-ray absorption fine structure (EXAFS)), The XANES shows that Pt is electron-deficient even after reduction with hydrogen, Fourier transforms of k(1) and k(3)-weighted EXAFS results indicate the presence of Pt-O and Pt-Pt pairs in the Pt/SO42--ZrO2. On the basis of XAFS, the reported contradictory results that Pt is metallic by XRD analysis and Pt is in a cationic state by XPS are explained by the model that oxidized platinum particles with a metallic core are present in the Pt/SO42--ZrO2 even after the reduction.