The electronic state and site structure of doped S to enable photocatalysis of TiO2 under visible light were investigated using S K-edge XANES compared to theoretically generated spectra. S sites substituting on the O atoms of TiO2 were predominant and essential in photocatalysis based on S K absorption edge peak energy and post-edge pattern. Minor cationic/elemental S sites were detected as peaks clue to the transition to vacant level of S3p, but most were lost during photocatalysis.