A foil seal lamp in which even when a high temperature of the seal area is reached oxidation of the molybdenum metal foils and the molybdenum outer leads which have been placed in the seal area can be reliably prevented, and in which a long service life can be obtained. is achieved by providing the surfaces of the metal foil and the outer lead which are placed in the seal areas with protective coatings of crystalline molybdate. An increase in the amount of protective coating that can be carried is produced by surface roughening the outer leads.