Abstract: A vacuum degassing method wherein a molten substance at an elevated temperature in a storage tank is sucked to a vacuum degassing vessel through an uprising pipe connecting the storage tank and the vacuum degassing vessel by maintaining the vacuum degassing vessel at a negative pressure, the molten substance is degassed and the degassed molten substance falls to a guiding duct through a downfalling pipe connecting the vacuum degassing vessel and the guiding duct characterized by that a first flow quantity of the molten substance rising in the uprising pipe is restrained and a second flow quantity thereof falling in the downfalling pipe is controlled thereby maintaining a quantity of the molten substance in the vacuum degassing vessel at a pertinent level.