To provide a technology which can reduce the exhaust noise sufficiently.

In this exhaust structure 30 of jet propulsion boat, an auxiliary muffler 70 is provided at the top part of a reverse U-shape of connection pipe 60, and the auxiliary muffler 70 is set at the position higher than an exhaust pipe 32, in a jet propelling boat in which a jet propeller 20 to inject the water sucked from the boat bottom to the rear side; and an engine 15 to drive the jet propeller 20; are installed to the boat body, and a muffler 40 and the reverse U-shape of connection pipe 60 are connected on the way of the exhaust pipe 32 of the engine 15 in this order. As a result, even though the water invades in the exhaust pipe 32, the water invaded in the exhaust pipe 32 can be blocked by the connection pipe 60, and the water never invades in the auxiliary muffler 70 installed at the top part of the connecting pipe 60.