PURPOSE: To prevent the deposition of fluorescent material produced in a DC lighting type metal halide lamp of a heavy tube wall load by a simple construction.

CONSTITUTION: An electrode 102a becomes a cathode and an electrode 102b becomes an anode. Respectively the cathode 102a is made of an electrode shaft 203 of 10mm in length and 0.7mm in thickness whose material is tungusten- thorium alloy containing thorium, and the anode is made of the electrode whose tip portion 222 is expanded up to 1.5mm diameter. The distance L of the electrodes between the cathode 102a and the anode 102b is set to be 6mm, and one side metal foil conductor 106 connected to the anode 102 is electrically connected so as to be same potential with a reflector 110.