To provide a screen device that can completely eliminate suspended matters from a jet water suction port in a water jet propulsion boat.

In a water jet propulsion boat, a jet water suction port 6 provided at the boat bottom is provided with a screen 7 formed by overlapping fixed grids 7b and movable grins 7c, and each movable grid 7c provided between the fixed grids 7b is rotated downward in relation to the fixed grids 7b. Dirt and the like caught by the screen can be separated by rotating the movable grids 7c downward, and the separated dirt and the like can be washed away backward by the advance of a hull.