PURPOSE: To improve removal of flat particles by arranging a scraping means below a lower side of a return travelling part of a belt and liquid injection nozzles at a position immediately before a contact point of the scraping means and the belt.

CONSTITUTION: A slender hollow beam 1 is provided below a conveyor belt 2, one or a plural number of scraping means 5 are installed and liquid injection nozzles 4 are installed. This scraping means 5 is arranged so that a tip 8 on a head and makes contact with a lower side surface of the conveyor belt 2. A large number of nozzles 4 are provided by communicating them to an inside reserver 4A of the beam 1, and they are arranged so that liquid in the reserver 4A is injected to the lower side surface of the belt 2 toward immediately before a contact position or the constant position of the belt 2 and the scraping means 5. A deflecting plate 9 to deflect dust and liquid dropping from the belt 2 is provided.