Photocatalytic NOx oxidation and storage on photocatalysts were investigated with the aim of an efficient NOx abatement at low temperature. TiO2 photocatalyst exhibited a sufficient NOx storage capacity under UV light irradiation even at room temperature, and the modification of Ba on TiO2 as a NOx trapping agent greatly enhanced the activity. Several spectroscopic methods revealed that dispersed Ba species on TiO2 were effective for NOx storage.