A xenon lamp in which fluctuation of the arc can be suppressed and the time until formation of the flicker phenomenon delayed by having an anode with a flattened or rounded anode tip, a rounded or flattened back end; a portion with a diameter that gradually increases from the anode tip toward the back end of the anode; a portion with a decreasing diameter located behind the portion with the increasing diameter of an axial length which is greater than the length in the axial direction of the portion with an increasing diameter; and a portion with a maximum outside diameter formed in a transition area between the portion with the increasing diameter and the portion with a decreasing diameter, and that the transition area between the portion with the increasing diameter and the portion with the decreasing diameter is formed to be continuous.