PURPOSE: To obtain lower priced and certain air-tight sealing without any generation of impurity gas by making air-tight sealing of both ends of a transparent ceramic tube to be a luminous tube with closing bodies through glass solder of granular shape.

CONSTITUTION: A closing body 2 making contact with and disposed at the opening end of an alumina ceramic tube 1 is made of Niobium metal, thermal expansion coefficient of which is similar to that of alumina ceramic. A metal tube 3 made of Niobium metal is pressed and sealed air-tightly at its one end and the bottom end of an electrode 4 is mounted at the other end. Glass solder 5 of alumina, calcia etc. being as a main component is formed in granular shape of a diameter being approximately 1W5mm and is filled within the gap between the internal surface of a flange portion 2a of the closing body 2 and the external surface of the end portion of the transparent alumina ceramic tube 1. This, being positioned, for an instance, at a bottom side so that the glass solder 5 should not be separated, is heated at about 1,400W1,500°C by a heater etc., in vacuum or inert gas, then is cooled gradually, the glass solder 5 is melted, filled up within the gap between the alumina ceramic tube 1 and the closing body 2, then solidified and a certain air-tight sealing state can be obtained.