A high-pressure mercury lamp is provided that includes a transparent envelope
made
of quartz glass, in which mercury, halogen, and a rare gas are sealed and a pair
of electrodes provided in the transparent envelope. The amount of the halogen sealed
in the transparent envelope is in the range from 1.010-6 mol/mm3
to 1.010-2 mol/mm3, and 2.5 mol % to 25
mol % of oxygen with respect to the amount of the halogen is present in the transparent
envelope. The high-pressure mercury lamp can prevent blackening of an inner wall
of the transparent envelope from occurring over a long period of lighting without
deteriorating the startability or lamp characteristics, thus achieving a long life.
