In order to improve the photocatalytic decomposition activity of benzene, which has been regarded as a typical volatile organic compound in air, TiO₂ catalysts modified with metals (Pt, Cu, and Fe) were prepared and tested. Certain correlations between the photocatalytic activities and the optical properties of those catalysts were also found and discussed by using UV-visible spectroscopy and a photoluminescence spectroscopy. Among the metal impregnated TiO₂, the Pt impregnated TiO₂ showed the best activity and it was even better than that of P-25 which is widely used in commercial applications. For the various metal impregnated TiO₂ samples, certain proportional relationships were found between the observed photoluminescence values and photocatalytic activities. On the other hand, in UVvisible spectra for metal impregnated TiO₂ samples, the transmittance value was reduced depending upon the loading of metals. It was thought that photocatalytic activity increases from initial reaction state because the number of photoexcited electrons, which exist at Pt surface augment due to the band gap energy change of Pt and TiO₂ by sintering and light energy-absorbed electrons excited easily to conduction. In conclusion, it was confirmed that the enhanced photocatalytic activity for high metal loading on TiO₂ is related with the high concentration of excited electrons, which could be monitored through UV-visible spectra.