To improve the sealing performance of an exhaust pipe extending from one side to the other side of a member at the side of an engine.

This exhaust device for the outboard engine includes the exhaust pipe to form a catalyst exhaust passage extending from one side to the other side of a guide exhaust 2, and a catalyst 33 provided in the exhaust pipe, the guide exhaust 2 having a through-hole 30 at the rear end. The exhaust pipe is composed of an upstream side exhaust pipe 31 extending from the exhaust outlet of the guide exhaust 2 to the through-hole 30, and a downstream side exhaust pipe 32 extending from the exhaust inlet of the guide exhaust 2 to the through-hole 30. The downstream side end of the upstream side exhaust pipe 31 is fitted to the upstream side end of the downstream side exhaust pipe 32 movably in the through-hole 30. A metal O-ring 63 is held between the downstream side end and the upstream side end.