PURPOSE: To obtain a compact display tube having sufficient strength by welding a frame type side member integrating powder glass by baking to a plate glass segment and assembling substrate which will form a display window.

CONSTITUTION: A soda lime glass used as a window glass is broken into fragments and these are placed into a mold made of graphite. These are then heated under the nitrogen gas ambient and is baked. Thereby, a frame type side surface glass mold 5 can be manufactured. A low melting point powder glass 6 is pressurizingly deposited on the surface of said frame side surface glass mold 5. A liquid obtained by dissolving an acrylic resin with an organic solvent is previously mixed to such powder glass in view of assuring moldability. Such powder glass is sequentially sent to the belt type electric furnace for sintering and hardening. A substrate assembly 4 is placed to the lower end part of mold 5, while a display window 1 is placed to the upper end surface. When it is heated again, the low melting point powder glass sintered material is perfectly fused and vitrificated, forming a hermetical sealing case.