SrTiO 3 photocatalysts doped with chromium ions showed photocatalytic activities for H 2 evolution from an aqueous methanol solution under visible light irradiation. However, it had a long induction period. Codoping of niobium or tantalum ions with chromium ions shortened the induction period, and increased the photocatalytic activities in respect of the H 2 evolution. The photocatalytic activities of chromium- and chromium/tantalum-doped SrTiO 3 were improved when they were pretreated at 773K in the hydrogen reduction atmosphere. Codoping of tantalum ions suppressed the formation of Cr 6 + ions and oxygen defects which would work as nonradiative recombination centers between photogenerated electrons and holes, resulting in the shortening of induction periods and the improvement of photocatalytic activities.