A vacuum degassing apparatus (10) for molten glass according to the present invention comprises a vacuum housing (12) where a vacuum is created; a vacuum degassing vessel (14) housed in the vacuum housing to degas the molten glass; an introduction device communicated to the vacuum degassing vessel so as to introduce untreated molten glass into the vacuum degassing vessel, or preferably an uprising pipe (16); and a discharge device to discharge treated molten glass from the vacuum degassing vessel, or preferably a downfalling pipe (18). In the apparatus, at least a portion of at least one of the vacuum degassing vessel (14), the uprising pipe (16) and the downfalling pipe (18) that in use directly contact the molten glass is constituted by refractory material having a porosity of not greater than 5%. The apparatus can increase quantity of flow of the molten glass and consequently a degassing throughput of the molten glass in comparison with prior art, having the same size and the same pressure loss. The apparatus can further increase the quantity of flow and the degassing throughput without making the size of the apparatus excessively larger.
Also disclosed is a parallel arrangement of vacuum degassing apparatus comprising a plurality of vacuum degassing units (102,104), a merging unit (150) and a stirrer (156), including a pressure equalising pipe (142) provided between said units.