A highly reliable ultra-high pressure mercury discharge lamp with a low risk of breakage of the quartz tube. The ultra-high pressure mercury discharge lamp includes a light emitting tube 2 in which a pair of electrode systems 24a, 24b is enclosed within a quartz tube. The pair of electrode systems 24a, 24b is outfitted with an electrode 21a, 21b having a weld 21a-2, 21b-2, a metal strip 22a, 22b with one end that is welded to the weld 21a-2, 21b-2, and a connection line 23a, 23b connected to the other end of the metal strip 22a, 22b. An aperture portion 22a-1, 22b-1 is provided in the metal strip 22a, 22b in the area surrounding the weld 21a-2, 21b-2.