The photocatalytic decomposition of water on various mixed metal oxides showing tunnel or layered structures has been investigated and their catalytic performance has been evaluated by the rates of hydrogen production under the irradiation of a mercury lamp and sunlight. It was found that the photocatalytic activity depends significantly on catalyst structures and on modification techniques, such as loading, proton-exchange or substitution, and tunnel oxides were superior to layered one with respect to the hydrogen production from water. The activity was enhanced by loading Pt and RuO2 for various mixed metal oxides, while it depended on the loading methods and the structure of catalysts. The comparison of the rates of hydrogen production under the mercury lamp and sunlight irradiations suggested that the hydrogen production under the irradiation of sunlight was almost attributed to the UV-light. The influence of Pt-loading methods and treatment with HNO3 on the activity and structure of catalysts has been also discussed in this study.