To create a decomposition catalyst for the several pollutants with the necessary performance, we united noble metals of two and three different types by selective and successive deposition, onto select mixed metal oxide supports. The catalytic oxidations of H-2, trimethylamine, o-chlorophenol and of dioxin derivatives over these multi-component noble metal catalysts were subsequeritly investigated. The ternary component catalyst, Au/Fe2O3-Pt/SnO2-Ir/La2O3, showed greatly enhanced activity in the catalytic oxidation of o-chlorophenol and of dioxin at 423 K, indicating a catalytic activity enhancing (boosting) effect by the addition of the Ir/La2O3 catalyst that by itself shows low activity.