A high pressure discharge lamp according to the present invention is a
high pressure discharge lamp in which the top ends of a pair of
electrodes opposed in a discharge vessel 2 of an arc tube 1 are formed
each into a substantially semispherical shape and a protrusion 10 to form
an arc spot is formed at each top end, wherein all of the relation:
0.3.cndot..cndot.L/I.cndot..cndot.1.0 for an inter-electrode distance
L(mm) between the electrodes and a lamp current I(A) during stable
lighting, the relation:
1.2.cndot..cndot.10.sup.-7.cndot..cndot.X/Y.cndot..cndot.1.1.cndot..cndot-
.10.sup.-5 for a molar amount X(mol) of bromine in the bromide sealed in
the discharge vessel 2 and an inner volume Y(ml) of the discharge vessel
2, and the relation: 9.cndot..cndot.W.sup.3/2/I.cndot..cndot.65, for a
weight W(mg) of tungsten at the top end of each electrode 3 formed into a
substantially semispherical shape are satisfied, and the lighting
frequency of a rectangular wave during stable lighting is 45 Hz or
higher.