In a mercury-free arc tube, regions including molybdenum foils 17 of electrode assemblies each of which is formed by connecting and integrating an electrode 16, a molybdenum foil 17, and a lead wire 18, are pinch-sealed where the electrode 16 projects inside a closed glass bulb 12, which encloses luminescent substances, etc. The molybdenum foil 17 is doped with or coated with TiO2 in the form of discontinuous lands and subjected to surface roughening by etching including oxidation and reduction. TiO2 particles or a TiO2 layer exposed on the rough surface 17c of the molybdenum foil 17 increases chemical joining strength to glass and makes deeper, more complicated minute unevenness 17b on the molybdenum foil surface to increase the mechanical joining strength to glass, so that even when a heat stress occurs at the interface between the molybdenum foil and glass in the pinch-sealed portion, foil floating does not occur.