To effectively remove foreign matter contained in molten metal and also, to improve a maintenance service of an oxide convection preventive plate provided with a filter member part.

The oxide convection preventive plate 3 is formed of a guide plate part 3A formed as a thick flat plate-state, molten metal passing-through hole part 3B penetrating the guide plate part 3A and filter member part 4 disposed in the molten metal passing-through hole part 3B. The guide plate 3A in the oxide convection preventive plate 3 is disposed so as to be freely attachable/detachable to/from a melting vessel 1, and the melting vessel 1 is divided into a melting portion 7 and a holding portion 8. The upper part 3F of the oxide convection preventive plate 3 is disposed at the upper position from the surface X-X of the molten metal formed in the melting vessel 1 and also, the upper end part 4D of the filter member part 4 is disposed at the lower position than the molten metal surface X-X.