A clean bench comprising a worktable on which polycrystalline silicon is placed, a box part which includes side plates to surround three sides except a front face of a working space above the worktable, and a ceiling plate which covers an upper side of the working space. Supplying holes are formed in the ceiling plate of the box part, which supply clean air onto an upper surface of the worktable. An ionizer is provided, which ionizes the clean air supplied from the supplying holes to the working space and removes static electricity on the worktable. Suction holes are formed in the side plate of the box part, which suction air from the working space.