Mutual the supply opening 26 and the upper surface 14 and both surfaces 13 and 14 disposed by facing the when 13 of the upper structure body 10, and the counter of the lower structural body 11 having an exhaust port (30) It is ejected from the supply opening (16) in the processing space 15 is formed between an etching process on the bottom (3a) of the glass sheet 3 to be conveyed in the horizontal direction by the processing gas (5) sucked into the exhaust port 30 also and at the same time, it is positioned to separate the supply opening 26 and the exhaust port 30 in the glass sheet 3 transport direction. And a process gas flow area in the direction downstream side of the lower structural body 11 of the upper surface 14 has the upper surface portion 22 of the top level of the area to the exhaust port (30), supply opening 26, an exhaust port (30) in is higher than the upper surface portion (18ab) of the highest.