PURPOSE: To elongate a life of a device by forming exhaust gas stirring slits on a plate provided with a catalyst, which slits are distanced from a welding portion on sides of the plate, and thereby improving connection strength of the welding portion of the plate provided with catalyst.
CONSTITUTION: A plate 17 provided with an exhaust gas purifying catalyst is longitudinally welded to an inner peripheral portion of an exhaust pipe 12 of a muffler 11. Exhaust gas stirring slits 17d are formed on plate elements 17a, 17b of the plate 17 provided with catalyst, excluding a welding portion 17c. The slits 17d are formed in plural in the longitudinal direction of the plate 17 provided with catalyst. Neither a cutout nor a hole is formed on the welding portions on both sides of the plate 17 provided with catalyst, so that certain welding is carried out over a whole length of the welding portion. High connection strength is thus secured, and a life of an exhaust system is elongated.