PURPOSE: To provide a water jet propelling machine which can be made lighter in weight and reduced in manufacturing cost because a liner is not applied to an impeller housing accommodating an impeller, and has no possibility of electrolytic corrosion, and can further heighten hardness by means of a spray deposit film.

CONSTITUTION: An impeller housing 3 and a nozzle 4 are connected to the rear side of an intake duct 1, and an impeller 7 connected to the rear end of a driving shaft 5 rotatably constructed through the intake duct 1 is arranged inside an impeller housing 3, and hard almite treatment is executed on the surface of the impeller housing 3 cast of light alloy, and a ceramic hard spray deposit film 9 is formed on a part to be the outside of the impeller 7 in the inner periphery of the impeller housing 3.