Ag+/ZSM-5 catalysts were prepared by an ion-exchange method and characterized by in-situ XPS, XAFS (XANES and EXAFS), UV-Vis, photoluminescence, and FT-IR investigations. These Ag+/ZSM-5 catalysts were found to exhibit an UV absorption band at around 190 nm due to the isolated Ag+ ions. The addition of N2O molecules leads to a shift in this band to 220 nm due to the adsorption of N2O on the Ag+ ions. The adsorption of N2O on the Ag+ ions could also be clarified by the appearance of characteristic FT-IR bands at 2251 cm(-1). UV irradiation of the Ag+/ZSM-5 catalysts in the presence of N2O led to the photocatalytic decomposition of N2O into N-2 and O-2 at temperatures as low as 298 K. It was found that UV light at around 200-250 nm is effective for the reaction, suggesting that excitation of the isolated Ag+ ion plays a significant role in the photocatalytic decomposition of N2O.