A catalyst for converting harmful reductive and oxidative gases in exhaust gases into innoxious gases is provided. The catalyst essentially consists of a perovskite oxide represented by the general formulaLa.sub.(1-x)/2 Sr.sub.(1+x)/2 Co.sub.1-x Me.sub.x O.sub.3in which Me is an element such as Fe, Mn, Cr, V or Ti and x is a number of from 0.15 to 0.90. In order to fabricate durable catalysts, the catalytic component is supported on heat-resistant expanded metal or inorganic fiber meshworks or hollows cylinders of heat-resistant anti-corrosion metals or refractory materials with or without catalyst-bearing pellets.