To provide a jet propulsion boat having the narrow intervals of a right and left pair of foot steps and excellent maneuverability, by laying out an oil tank and an oil filter so that narrow engine width can be maintained, when a drysump method is adopted as an oil circulation method for a 4-cycle engine.

In a jet propulsion boat equipped with an astride type seat 15 and a right and left pair of foot steps positioned on both the sides of the seat 15, and loading a multicylinder 4-cycle engines 20, wherein a crank shaft 28 is extending in the front and rear direction of a boat body 10, in the boat body at the position of the seat lower part; an oil tank 45 is arranged in one side of the engine 20, and an oil filter 46 is arranged, in one side of the engine 20 at the position of the front or rear sides of the tank 45.