<p>There is provided a light emitting tube having an airtight vessel made of translucent ceramics used for a high-voltage discharge lamp. The light emitting tube includes an airtight vessel (1) made of translucent alumina polycrystal ceramics, a pair of electrodes (2) arranged in the airtight vessel, and ionization medium put into the airtight vessel. The airtight vessel has a surrounding portion (1a) surrounding a discharge space (1c) and a pair of small-diameter cylindrical portions (1b) extending from the both ends of the surrounding portion in the tube axis direction. The rectilinear transmission ratio of the light in the surrounding portion is greater than the small-diameter cylindrical portion and exceeds 20%.</p>
