PURPOSE: To suppress total weight of exhaust pipes even when an exhaust device having a changeover valve is adopted to a multicylinder engine, and suppress a manufacturing cost.

CONSTITUTION: An exhaust passage changeover valve 12 which has a valve body for selecting one of upper and lower branch passages is arranged in an exhaust passage of each cylinder. A control device 10 is connected to each valve body for switching the branch passages while turning in the same direction according to an engine operation condition. The upper branch passages of the exhaust passage changeover valves 12 are connected to a low speed area exhaust pipe 20, while the lower branch passages are connected to a high speed area exhaust pipe 21. Only two expansion changers, for low speed and high speed, are required irrespective of number of the cylinders. Light weight and a low manufacturing cost are brought about.