An agitating device for agitating the exhaust gas of an engine includes a base plate having a plurality of through holes that are defined by radially extending spoke portions and a ring-like rim portion and are arranged in a circular pattern in a circumferential direction of the base plate, and a plurality of fins expanding from the respective spokes on a slant with respect to the base plate. The base plate is fixed in the exhaust passage by the rim portion being jointed to the exhaust passage at welded portions. The welded portions are each disposed in an area between respective two adjacent spoke portions in the circumferential direction of the base plate, and an outer edge of the rim portion positioned on the outer side of the rim portion in extending directions of the spoke portions is located next to the exhaust passage with a gap provided therebetween.