Reformer tube for converting hydrocarbon-containing input materials, preferably natural gas, into a synthesis gas product comprising carbon oxides and hydrogen under steam reforming conditions, comprising (a) an outer, pressurized shell tube, wherein the shell tube is divided into a reaction chamber and an exit chamber by means of a separating tray, so that it is possible to set a different, preferably lower, pressure in the exit chamber than in the reaction chamber, and wherein the reaction chamber is externally heated, (b) a dumped bed of a steam-reforming-active solid catalyst arranged in the reaction chamber, (c) an entry for the input gas stream comprising the input material, arranged in the region of the reaction chamber, wherein the entry for the input gas stream is in fluid connection with the dumped catalyst bed, (d) at least one helically coiled heat exchanger tube arranged inside the reaction chamber and inside the dumped catalyst bed, whose entry end is in fluid connection with the dumped catalyst bed and whose exit end is in fluid connection with the exit chamber, wherein the input gas stream after entry into the reaction chamber initially flows through the dumped catalyst bed and subsequently flows through the heat exchanger tube in countercurrent, and wherein the heat exchanger tube is in a heat exchange relationship with the dumped catalyst bed and the input gas stream flowing therethrough, (e) a collection conduit for the synthesis gas product, which is in fluid connection with the exit chamber, characterized in that, in the region of the exit chamber, (f) the exit end of the heat exchanger tube is fed through the separating tray and opens into an inner tube which is arranged in the interior of the shell tube and is in fluid connection with the collection conduit, so that the synthesis gas product is able to pass from the reaction chamber via the exit chamber into the collection conduit, (g) the inner tube is equipped with a corrosion protection layer or consists of a corrosion-resistant material, (h) a gas-permeable thermal insulation layer is disposed between the inner wall of the shell tube and the outer wall of the inner tube. (a) an outer, pressurized shell tube, wherein the shell tube is divided into a reaction chamber and an exit chamber by means of a separating tray, so that it is possible to set a different, preferably lower, pressure in the exit chamber than in the reaction chamber, and wherein the reaction chamber is externally heated, (b) a dumped bed of a steam-reforming-active solid catalyst arranged in the reaction chamber, (c) an entry for the input gas stream comprising the input material, arranged in the region of the reaction chamber, wherein the entry for the input gas stream is in fluid connection with the dumped catalyst bed, (d) at least one helically coiled heat exchanger tube arranged inside the reaction chamber and inside the dumped catalyst bed, whose entry end is in fluid connection with the dumped catalyst bed and whose exit end is in fluid connection with the exit chamber, wherein the input gas stream after entry into the reaction chamber initially flows through the dumped catalyst bed and subsequently flows through the heat exchanger tube in countercurrent, and wherein the heat exchanger tube is in a heat exchange relationship with the dumped catalyst bed and the input gas stream flowing therethrough, (e) a collection conduit for the synthesis gas product, which is in fluid connection with the exit chamber, characterized in that, in the region of the exit chamber, (f) the exit end of the heat exchanger tube is fed through the separating tray and opens into an inner tube which is arranged in the interior of the shell tube and is in fluid connection with the collection conduit, so that the synthesis gas product is able to pass from the reaction chamber via the exit chamber into the collection conduit, (g) the inner tube is equipped with a corrosion protection layer or consists of a corrosion-resistant material, (h) a gas-permeable thermal insulation layer is disposed between the inner wall of the shell tube and the outer wall of the inner tube.