Abstract: With regard to a metal vapor discharge lamp with a triple tube structure including a discharge tube, an inner tube, and an outer tube, misalignment of axes of the inner tube and the outer tube is prevented. The metal vapor discharge lamp (14) is composed of a discharge tube (30) having a pair of electrodes therein, an inner tube (32) having a pinch-sealed part (86) at an end thereof and hermitically housing the discharge tube therein, and an outer tube (34) housing the inner tube therein, and a base (36). In a clearance between the inner tube and the outer tube, there disposed a restrain member (37) for restraining movement of the inner tube relative to the outer tube in a direction orthogonal to an axis of the metal vapor discharge lamp.