To enable allocation and high densification of a display pattern to be freely realized on an anode board and eliminate wasteful consumption of energy.

On an anode board 7 constituted by forming a leading wire 2 and a display segment 6 on the surface of an insulating board 1, a control electrode 9, a support body of a filament 8, and lead pin 10 are fixed, and an anode board assembly 11 is formed. The first silver printed thick film 12 is formed at the top part opening end of a frame shaped spacer glass 13. The bottom part opening end of the spacer glass 13 is sealed at the peripheral edge part on the anode board assembly 11 by means of a flit glass 14. The anode board assembly 11 in which the spacer glass is sealed, the face glass 16, and a low-melting point metal body 17 are stored in their specified position in a vacuum chamber. The inside of the vacuum chamber is heated at a specified degree of vacuum, and the low-melting point metal body 17 is welded it between the first silver printed thick film 12 and the second silver printed thick film 15 and sealed.