For the production of a catalyst body for the catalytic treatment of gas, in particular for the purification of exhaust gas, flat and corrugated sheet metal members having a metallic core and coatings are formed, which coatings comprise a nonmetallic wash coat and at least one catalytically active noble metal. A packet comprising sheet metal members having coatings is then arranged between two walls of a sleeve. Thereafter, each edge of each sheet metal member, which edge faces one of the two walls, is welded to the relevant wall in at least one edge segment. The sheet metal members adjacent to one another then together bound passages for the exhaust gas. This production process makes it possible, even in the case of small cross-sectional dimensions of the passages, to apply uniform coatings to the entire surfaces of the sheet metal members, said surfaces bounding the passages.