Provided is a metal halide lamp capable of being dimmed, which is
prevented from non-lighting due to leakage of an arc tube attributable to
a crack occurring at thin tubes, as well as realizing a desired color
characteristic. The metal halide lamp has an arc tube that includes an
envelope made of translucent ceramic, a pair of electrodes, and metal
halides, the metal halides including rare earth metal halide, sodium
halide, and magnesium halide, the rare earth metal halide being at least
one of dysprosium halide, thulium halide, holmium halide, cerium halide,
and praseodymium halide, and the magnesium halide being at least one of
magnesium iodide and magnesium bromide, where when a maximum lamp power P
(W) is in a range of 70 W to 250 W, the following relations are
satisfied: 0.0345A+0.0028B<0.0015 P+0.0475; A.gtoreq.0.021P+0.313; and
B.gtoreq.10.0, where A (mg) represents a total content of the metal
halides, and B (mol %) represents a content ratio of the magnesium halide
to the metal halides.