Cu(I)SAPO-5 catalysts prepared by a combination of ion-exchange and an evacuation treatment at high temperatures were found to exhibit a fairly high photocatalytic activity for the decomposition of N2O into N-2 and O-2 under UV-light irradiation at 298 K. In contrast to other Cu(I) catalysts, such as Cu(I)ZSM-5, the coexistence of H2O in the reaction system of the Cu(I)SAPO-5 scarcely affected the photocatalytic activity. The relationship between the photoluminescence behavior due to the presence of Cu(I) species and the photocatalytic activity of Cu(I)SAPO-5 have been investigated as a function of the Si/Al ratio, showing that the excited state of the Cu(I) species plays a significant role in the photocatalytic reaction as an active site for the reaction.