An emission device for an ultra-high pressure mercury lamp which maintains an electrode tip shape by which a stable discharge can always be carried out is achieved for a short arc ultra-high pressure mercury lamp with silica glass arc tube containing a pair of opposed electrodes spaced apart a distance of at most 2 mm and in which the arc tube is filled with at least 0.15 mg/mm.sup.3 of mercury, a rare gas and a halogen in the range from 1.times.10.sup.-6 .mu.mole/mm.sup.3 to 1.times.10.sup.-2 .mu.mole/mm.sup.3; by providing an operating device which produces a current feed by which the surface of the tip of at least one of the electrodes is shifted into a molten state during lamp operation.