A catalytic exhaust cleaning device for a high-power multi-cylinder engine of the type including independent carburetors and exhaust pipes for the respective cylinders. The exhaust pipes are interconnected for fluid communication therebetween at locations upstream of the respective catalytic converters arranged therein so that the latter are evenly fed with exhaust gases of substantially the same composition and volume and with substantially equal amounts of secondary air and operate effectively with substantially the same high efficiency. The exhaust communicating pipe interconnecting two adjacent exhaust pipes is divided into two sections, which are fixed at one end to the respective exhaust pipes and held at the other end in aligned abutting relation by a radially expansible tubular joint member, which is fixed to one of the two pipe sections and clamped against the other section. This structure not only facilitates assembly of the communicating and exhaust pipes but effectively prevents any thermal deformation of the communicating pipe.