To provide an exhaust device formed such that a fourcycle engine is arranged in a compact manner in an engine room togetherwith an exhaust pipe and further, mold constitution, such as an exhaust pipe core and a main mold, is simplified to facilitate manufacture, division bodies are respectively integrally molded by casting, and further, when the division bodies are integrally assembled together, the assembly is formed in a circular in cross section and a peripheral length is minimized, manufacture of a seal member is facilitated, and the periphery of an exhaust pipe is reliably sealed.

An exhaust device formed such that exhaust pipes 21-24 and a water jacket housing to cover the peripheries of the exhaust pipes are integrally arranged comprises two division bodies 7A and 7B, and the division bodies 7A and 7B are respectively integrally molded by using an aluminum alloy through sand mold casting. On the division surfaces (mating surfaces) 7C of the division bodies 7A and 7B, flanges 7a and 7b are formed at a whole except an exhaust port part 25 and at the peripheries of the circular joining spots of the exhaust pipes 21-24, and a number of screw holes 7c for coupling and bolt through-holes 29 for mounting on an engine are formed in proper spots.