PURPOSE: To facilitate the manufacture of an airtight terminal without packing air bubbles by flattening the upper surface of glass in a primary sealing process using a stepped section formed with difference in the inner diameter of a metal outer ring.

CONSTITUTION: The first glass 24b having a ratio of height h1 to outer diameter d1 less than 2.5 is positioned at an area within a metal outer rig 23 having a plurality of sealing inner diameters D1 and D2 via a stepped section 23a, up to height H1 and at the inner diameter D1. This glass 24b is heated and melted for sealing up to the stepped part 23a, and the surface thereof is flattened. Furthermore, the second glass tablet 24c having a ratio of height h2 to outer diameter d2 less than is melted for sealing on the first glass 24b in the metal outer ring 23, up to height H2 and at the inner diameter D2. According to the aforesaid construction, an airtight terminal can be manufactured without trapping air bubbles inside.