Catalytic activities of perovskite-type La0.8Sr0.2M1-2yIII CuyRuYO3 (M-III = Al, Mn, Fe, Co) for CO oxidation and CO-NO reactions were changed significantly by simultaneous Cu/Ru substitution, depending on the host M-III cations. Cu/Ru substitution caused the decrease of both activities (Co) and the preferential promotion of activity for CO oxidation (Fe) or the GO-NO (Mn) reaction. When the Cu/Ru pair was substituted in inert La0.8Sr0.2AlO3, the catalytic activities for both reactions increased remarkably, and the resulting La0.8Sr0.2Al0.8Cu0.1Ru0.1O3 Showed activity comparable to Pt/Al2O3 and La0.8Sr0.2CoO3. It is inferred that Cu and Ru ions in the Al-based perovskite promote, respectively, the reduction step of the catalyst by CO and the oxidation step of this reduced catalyst by NO.