PURPOSE: To efficiently compose impurities in waste gases by dispersing and depositing a catalytic component on active alumina compounded with a stabilizer selected from calcium sulfate, strontium sulfate and barium sulfate.

CONSTITUTION: A coating consisting of a mixture composed of active alumina and the bulk stabilizer which is substantially insoluble in water and is selected from a thermally stable quantity of the group of at least one kind among the calcium sulfate, strontium sulfate and barium sulfate is formed on a carrier base material consisting of an integrated honeycomb, foamed ceramics, metallic structure, etc. Further, a platinum group metal is deposited as the catalyst component on the coating, by which the catalyst is produced. The bulk stabilizer is compounded with the catalyst at about 0.5 to 50 wt.% of the weight of the active alumina. The platinum group metal is platinum, rhodium, palladium, iridium, ruthenium or osmium.