PURPOSE: To prevent blow holes in a product by making the height position of a molten metal discharging hole in a refined molten metal dropping chamber in this device higher than the lower face of a horizontal base plate.

CONSTITUTION: Vertical ceramic tubes 4 formed with an alumina-based porous tube are fitted in an erecting condition on a horizontal base plate 3 formed with a silicon carbide based refractory plate. Then, upper side of the tube 4 is closed with a closing member 5, and the lower side is opened 6 to form filtration unit 2. In the device for incorporating this filtration unit 2 in a filtrating vessel 1 and forming the refined molten metal dropping chamber 12 at the lower part of the base plate 3, the molten metal discharging hole 14 in the dropping chamber 12 is opened at the position higher than the lower face of the base plate 3. By this method, the molten metal 15 is refined at the time of passing through the tube 4 and the refined molten metal 15 is dropped into the dropping chamber 12 through throughholes 7 in the base plate 3 and taken out from the molten metal discharging hole 14 through a passage 13, and any space in the dropping chamber 12 is not formed. Therefore, drip phenomenon, with which the molten metal becomes drips and drops into the dropping chamber 12, is not occurred and the product having no blow hole is obtd.