TiO2 particles of various sizes were prepared by grinding in cyclohexanone, and TiO2 particulate films were obtained by depositing these TiO2 particles with various sizes onto a glass or quartz substrate. The effect of the particle size and thickness on the photocatalytic properties of the films was evaluated via oxidative degradation of gaseous 2-propanol. The initial rate of 2-propanol degradation under UV light irradiation for the films deposited with 30 nm TiO2 particles increased with increasing film thickness up to 600 nm, and reached a saturated value above this film thickness. Photocatalytic activity for the films with thickness below 600 nm was larger when smaller TiO2 particles were deposited onto the substrate, due to the increase in the surface area of the particulate films. Furthermore, saturated values of the photocatalytic activity for thick films were smaller for the films deposited with smaller particles, which is mainly attributed to the change in crystal form of the particles during the grinding treatment.