A high-pressure mercury lamp includes an arc tube, and a pair of electrodes is provided in a discharge space of the arc tube. In the discharge space, mercury and xenon gas are sealed. The amount of mercury per unit volume that is to be sealed in the discharge space is within a range of 0.12 mg/mm.sup.3 to 0.35 mg/mm.sup.3. A pressure of the xenon gas in the discharge space is within a range of 2.0.times.10.sup.5 Pa to 2.0.times.10.sup.6 Pa.