Abstract: A front exhaust pipe is connected to a front engine block, and a rear exhaust pipe is connected to a rear engine block. The front exhaust pipe extends from the front engine block downward, and curves and extends rearward. The rear exhaust pipe includes an upstream portion extending downward from a rear portion of the engine and a downstream portion extending forward from a lower end of the upstream portion and curving rearward. Rear ends of the front and rear exhaust pipes are joined together and connected to a main exhaust pipe. The rear and front exhaust pipe have substantially the same length. Therefore, vibration due to a difference between natural frequencies of front and rear exhaust pipes is reduced, and sound vibration performance is enhanced. Further, a declination of output due to disorder of exhaust pulsation in the confluence portion of the front and rear exhaust pipes is avoided.