PURPOSE: To make sealing of a glass tube body possible without using a special exhaust tube by providing a metal ball coated with solder glass at the exhaust port of the glass tube body and sealing the exhaust port after evacuating inside the glass tube body.

CONSTITUTION: A sealing metal ball 9 is prepared in such a manner that on the surface of a metal ball made of an alloy such as of Ni-Cr-Fe, an oxide film 7 is made up and a solder glass film 8 is formed thereon and after that the metal ball 9 is temporarily sintered. A glass tube body 1 having an exhaust port 4 disposed with the sealing ball 9 is arranged in a vacuum bell jar and after performing baking exhaustion the sealing ball 9 is heated with a high frequency heating coil 10. By this heating the solder glass film 8 on sealing ball 9 is melted and seals the exhaust port 4. By this method the glass tube body 1 can be sealed up without requiring any exhaust tube.