A discharge lamp which emits light by an electric disacharge by applying an AC voltage between a pair of ceramic cathodes (1) and has a long service life. Each ceramic cathode (1) is constituted of an electron emitting material (3) constituted of a conductive oxide having an aggregate type porous structure which contains a first component composed of at least one element selected out of Ba, Sr, and Ca, a second component composed of at least one element selected out of Zr or Ti, and a third component composed of at least one element selected out of Ta and Nd and a conductor or semiconductor layer which is formed on the surface of the conductive oxide and composed of at least one kind selected out of the carbide, nitride, and oxide of Ta or Nb and a bottomed cylindrical container (2) for storing the material (3). In a valve (4), in addition, an Ar, Ne, Kr, or Xe gas or their mixed gas is sealed under a pressure of 10-170 Torr.