Abstract: A catalytic converter apparatus for reducing pollutants from an engine having a plurality of cylinders. The converter apparatus has an upper casing for mounting on the engine and branch pipes extending to the engine and through which exhaust gas discharged from the respective cylinders in the engine is led. A lower casing is connected to the upper casing for forming an exhaust manifold in cooperation with the upper casing. The lower casing has a discharge port for the exhaust gas. A catalyst casing is disposed within the exhaust manifold and has a support member extending therefrom and held between abutting surfaces of the upper and lower casings. Bolts are inserted through the casings from above the upper casing for coupling the upper and lower casings to each other and clamping the support member therebetween.