A long-life high-pressure discharge lamp suffers reduced blackening and luminance
drop even after it has been turned on over a long period of time, and is arranged
to prevent the internal gases from leaking out and also to prevent the lamp bulb
from being ruptured. The high-pressure discharge lamp has a pair of confronting
electrodes inserted in a lamp bulb which confines therein at least mercury and
a halogen gas. The lamp bulb contains oxygen at a partial pressure lower than a
partial pressure which can maintain a luminance of 80% after 100 hours of operation
and equal to or higher than 1.010-;5 Pa.
