It was found that in a volatile organic compound (VOC) catalytic combustion reaction, the dispersion of the platinum catalyst that was supported on an anodized aluminum plate by the electrolysis supporting method, decreased with the reaction time. The sintering of the catalysts was explored by the respective catalytic combustion of benzene, toluene, and ethylbenzene. The dispersions of platinum varied with reaction atmospheres during the reaction. The results of activity tests showed that catalytic activity was promoted with sintering of platinum particles. From the analysis of temperature-programmed desorption (TPD), the surface characteristics of catalysts were studied. It was found that the amount of chemisorbed aromatic hydrocarbons increased along with the sintering of platinum particles. This was applied to elucidate the activating effect of sintering.