The inventio provides a long arc-type electric-discharge lamp which can be lighted by AC, a pair of electrodes are oppositely arranged in an elongated luminescent tube having ultraviolet transmission properties, rare gases and metals as luminescent materials are put in the luminescent tube, and the electrode contains rare earth oxide. The long arc-type electric-discharge lamp can inhibit the quick exhausting of an emitter (electronic radioactive substance), can avoid the blacken and whiten of the luminescent tube and can be lighted stably for long time. The long arc-type electric-discharge lamp is characterized in that, the average value of the lamp current is set as I(ampere: A), the volumn of the 3mm of front end of the electrode is set as V(mm3), 0.4<=(I/V)<=1.0 is satisfied.