To provide a duct collector which facilitates, especially, removal of foreign matter adhering to the screen at a suction opening while a boat is navigating, on the dust collector for the suction opening in a water jet propulsion device.

This water jet propulsion device 1 which obtains the propulsion force of a boat 15 by pressurizing water sucked in a suction casing 2 by means of the impeller 5 of a pump casing 4, and jetting pressurized water from a delivering casing 6, is formed so as to rotate freely by disposing a screen 8 at the inlet part 3 of the suction casing 2, and forming a receiving-blade-shaped screen grid at the screen 8, and bringing a cutter 9 jointed to a rotational drive device 10 into contact with the screen grid. The cross section shape of the screen grid is formed into a trapezoid one, so as to extend its contact surface side with the cutter 9.