An excimer discharge lamp includes an electric discharge container having a pair of plates which face each other and connected by a side wall. An electrical discharge space is formed between the plates. A pair of external electrodes are provided on exterior surfaces of the plates. A light emission gas of rare gas, halogen or halide is enclosed in the electrical discharge space. The pair of plates and the side wall are made of sapphire, YAG, or single crystal yttria. Impurities which exist in an inner surface of the electric discharge container surrounding the electrical discharge space contain at least silicon, carbon, or cerium, and the quantity thereof is 0.6 ng/cm2 or less.