TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Arrangement: The hydrodesulfurization device and modifier are arranged facing across the flow path. Catalyst layer (11) contains catalyst species having function to convert sulfur compound into hydrogen sulfide, and catalyst layer (12) contains catalyst species having function to adsorb hydrogen sulfide. By heat-transfer from the hydrogen-containing gas, catalyst layer (11) is set to temperature (I) at which reaction for conversion to hydrogen sulfide becomes predominant than reaction for adsorbing hydrogen sulfide, and catalyst layer (12) is set to temperature (II) lower than temperature (I). Catalyst layer (12) has a high-temperature adsorption catalyst layer and a low-temperature adsorption catalyst layer, arranged such that the hydrogen-containing gas is heated sequentially by high-temperature adsorption catalyst layer and low-temperature adsorption catalyst layer. The high-temperature adsorption catalyst layer adjoins catalyst layer (11), and the low-temperature adsorption catalyst layer is arranged across the high-temperature adsorption layer with a space. A mixed-gas flow path (56) is provided for mixed gas of source gas and water vapor, before flowing into the modifier. At least one portion of catalyst layer (12) is arranged such that the hydrogen-containing gas flowing through the portion adjoining the mixed-gas flow path through the partition is heated. A mild-heat-transfer portion comprising a heat insulating material and an air pocket is provided between the hydrodesulfurization device and partition. A transformer containing copper-zinc type catalyst which reduces carbon monoxide in the hydrogen-containing gas sent from the modifier by shift reaction, is provided. Catalyst layer (12) contains copper-zinc type catalyst and is located at the vicinity of the transformer. The low-temperature adsorption catalyst layer contains the copper-zinc type catalyst such that the layer is located at the vicinity of the transformer.