Cu(I) (Cu+) ion catalysts anchored onto various oxides (SiO2. Al2O3, Al2O3, and SiO2) were prepared by the combination of an ion-exchange method and a thermovacuum treatment. XAFS (X-ray absorption fine structure) investigations revealed that Cu+ ions exist as linear two-coordinate Cu+ on SiO2. Al2O3,while they exist as planar three-coordinate Cu+ on Al2O3 or SiO2. It was also found that the typical photoluminescence observed at 430 nm for the Cu+/(SiO2. Al2O3) catalyst and that observed at 510 nm for the Cu+/Al2O3 and Cu+/SiO2 catalysts could be attributed to the radiative decay from the excited electronic state of the linear two-coordinate Cu+ ions and planar three-coordinate Cu+ ions, respectively. The addition of N2O onto the Cu+ ion catalyst leads to the quenching of the photoluminescence of Cu+, indicating that N2O interacts with the photoexcited Cu+ ion. UV irradiation of the catalysts in the presence of N2O led to the formation of N-2 and O-2 at 298 K, indicating that the photocatalytic decomposition of N2O proceeds on the Cu+ ion catalysts. The reaction was found to proceed more efficiently on the Cu+/(SiO2. Al2O3) catalyst than on the Cu+/Al2O3 or Cu+/SiO2 catalysts, suggesting that the two-coordinate Cu+ species show higher activity for this reaction than the three-coordinate Cu+ species.