Using the ArF excimer laser-induced MOCVD method, InN x O y thin films are grown on a glass substrate. The photolytical decomposition of NH 3 enables to grow them even at room temperature. It is found that the InN x O y thin films grown at a temperature less than 250 1C show an excellent photocatalytic decomposition of H 2 S under UV irradiation, while the activity of the films grown at a temperature higher than 300 1C is very small, less than 1 4 of that for the low-temperature films. The excellent photocatalytic activity for the low-temperature films is closely related to the amorphous phase of the films. r