A high pressure sodium lamp including a light permeable arc tube and an electrode extending into the arc tube via a central aperture provided in the arc tube. The electrode is supported in the aperture by means of a glass solder sealing composition. Sodium amalgam is seated in the arc tube and condensed at a corner thereof. To prevent sodium amalgam condensed at the corner of the arc tube from contacting the glass solder filled in the central aperture of the arc tube, sodium amalgam including sodium of 10-30 (wt %) is sealed in the arc tube at a prescribed volume V (mm.sup.3) which substantially satisfies the following relationship: ##EQU1## where D (mm) is the diameter of the arc tube, d (mm) is the diameter of the central aperture, Vo (mm.sup.3) is the volume of the sodium amalgam sealed in the arc tube when the shortest distance between the sodium amalgam condensed at the corner and the glass solder filled in the central aperture is given by ##EQU2## and WL (W) is the lamp power.