Reformer furnace for catalytic reforming of a carbon-containing input material with steam, having a radiation space defined by a plurality of walls and delimited from the external surroundings, wherein the radiation space comprises a steel construction configured as a framework for the fastening of supply and discharge pipelines, burners and vertically arranged reformer tubes, wherein the burners are arranged to produce downwardly or upwardly directed flames for heating the reformer tubes, and wherein the burners and reformer tubes are arranged within the radiation space in rows as burner rows (201a, 201b) and reformer rows, wherein the burner rows (201a, 201b) and reformer rows are arranged in an alternating and parallel manner with respect to one another, and the steel construction has a plurality of main carrier units, wherein each main carrier unit has two wall-adjacently arranged, vertically extending supports (206a, 206b) and a horizontally extending main carrier which is connected via the supports and which extends over the entire length of the radiation space, and wherein the main carriers are configured for fastening the supply and discharge pipelines, burners and reformer tubes, and the steel construction has a plurality of horizontally extending crossmembers which connect the supports of the main carrier units among one another, characterized in that the main carriers of the main carrier units are arranged so as to run parallel to the reformer tube rows and burner rows (201a, 201b), and the crossmembers are arranged so as to run at least partially orthogonally with respect to the reformer tube rows and burner rows (201a, 201b). a radiation space defined by a plurality of walls and delimited from the external surroundings, wherein the radiation space comprises a steel construction configured as a framework for the fastening of supply and discharge pipelines, burners and vertically arranged reformer tubes, wherein the burners are arranged to produce downwardly or upwardly directed flames for heating the reformer tubes, and wherein the burners and reformer tubes are arranged within the radiation space in rows as burner rows (201a, 201b) and reformer rows, wherein the burner rows (201a, 201b) and reformer rows are arranged in an alternating and parallel manner with respect to one another, and the steel construction has a plurality of main carrier units, wherein each main carrier unit has two wall-adjacently arranged, vertically extending supports (206a, 206b) and a horizontally extending main carrier which is connected via the supports and which extends over the entire length of the radiation space, and wherein the main carriers are configured for fastening the supply and discharge pipelines, burners and reformer tubes, and the steel construction has a plurality of horizontally extending crossmembers which connect the supports of the main carrier units among one another, characterized in that the main carriers of the main carrier units are arranged so as to run parallel to the reformer tube rows and burner rows (201a, 201b), and the crossmembers are arranged so as to run at least partially orthogonally with respect to the reformer tube rows and burner rows (201a, 201b).