To provide a flat discharge tube capable of raising exhaust efficiency of a vacuum exhaust of air and air supply efficiency of discharge gas in one in which a discharge space is sectioned into a plurality of cells by dielectric ribs.

In the flat discharge tube 1, a plurality of the dielectric ribs 5 are interposed between both glass substrates 2, 3 as first and second dielectric flat plates forming the discharge space 6, and both ends of these dielectric ribs 5 in a longitudinal direction are connected with an inner wall side face of a frame glass 4. By this, the discharge space 6 is sectioned into a plurality of cells 6a to 6e. Groove parts 5b in the plural number are installed at a part of the upper face 5a of the plurality of dielectric ribs 5, and the cells 6a to 6e between the respective discharge sections are made communicated.