To provide an extra-high-pressure mercury lamp capable of surely preventing an easily electron-emitting substance from attaching to an inner wall of a discharge container and obtaining a long life of use, although an electrode structuring substance is prevented from attaching on an inner wall of the discharge container by using the easily electron-emitting substance.

The extra-high-pressure mercury lamp is equipped with an arc tube having a discharge space, and made by a pair of electrodes arranged opposed to each other and with 0.15 mg/mm3 or more of mercury and halogen sealed. A granular easily electron-emitting substance is included at least on one of the electrodes, a particle unit or a granular material consisting of an aggregate of a plurality of particles of the easily electron-emitting substance has an average particle diameter from 0.01 to 10 μm, a ratio being in a status aligning three or more among all granular particles with intervals of 15 μm or less along an electrode axis direction is 10% or less in a cross section including the electrode axis.