In this study, transition-metal-oxide bulk catalysts were prepared with the precipitation method to investigate their activity for the catalytic oxidation of volatile organic compounds (VOCs) (model VOCs: toluene and ethyl acetate), with an aim to develop a low-cost, safe, and highly effective substitute catalyst for noble-metal-based catalysts. A synergistic effect of copper and cobalt was observed over the Cu-Co oxide catalysts, which showed higher activity than either copper oxide or cobalt oxide alone. It is considered that in the Cu-Co catalyst, the fine dispersion of CuO particles on the surface of Co3O4, especially the formation of a Cu-Co spinel, probably causes an increase in the BET surface area and eventually enhances the VOC oxidation activity. When the 31 wt%Cu-44wt%Co catalyst was subjected to toluene catalytic oxidation, it gave a complete oxidation temperature of 200 degrees C, similar to that for a commercial 0.5 wt%Pt/Al2O3 catalyst. In ethyl acetate catalytic oxidation, dramatic activity was exhibited and the complete conversion temperature of 175 degrees C obtained over the 31 wt%Cu-44wt% Co catalyst was far lower than that for 0.5 wt%Pt/Al2O3 (ca. 300 degrees C).