Photocatalytic oxidation of benzene in air at room temperature was studied in order to obtain the information on its reactivity on the photoirradiated TiO2 catalyst. The objective of this paper is to describe in detail the dependence of the rate for benzene photoxidation on humidity, initial benzene concentration, and incident light intensity, since they are important factors for construction of VOC control system utilizing solar energy,,. The reaction mechanism is also discussed to understand the decomposition behavior of benzene.