To provide a dust separator that can remove foreign matter from a screen particularly even while sailing and cut the foreign matter into pieces regarding the dust separator for a suction port in a water jet propulsion device.

A grated screen is provided at a suction port of a suction casing of a water jet propulsion device. A scraper 10 is disposed at a suction face of this screen, and the scraper 10 is provided with back cutting edges 12. These back cutting edges 12 are fitted into screen grating, and the scraper 10 is disposed slidably in the longitudinal direction of the screen grating so as to tear off foreign matter adhering to a screen face and to cut and remove the foreign matter held in the screen grating. Flexible fibrous or stringy foreign matter can be cut into pieces by forming the cutting edge face of the scraper in hair clipper shape.