NOVELTY - An oxygen-containing gas (o) is mixed with source gas (f1) obtained by mixing steam and hydrocarbon group fuel in mixing chamber (8). Mixed gas is introduced to catalytic reaction chamber (5) via front chamber (9) maintained at preset temperature. Catalytic reaction chamber has catalytic portion (50) having catalyst (C1) rich in low-temperature oxidation activity, and catalyst portion (51) having catalyst (C2) rich in modification activity. Mixed gas is contacted with catalyst, and hydrogen-containing gas is produced by partial oxidation and water vapor modification.    USE - For manufacturing hydrogen-containing gas.    ADVANTAGE - The hydrogen-containing gas is stably produced, and decrease in catalytic activity due to carbon deposition is prevented.    DETAILED DESCRIPTION - An oxygen-containing gas is mixed with a source gas obtained by mixing steam and hydrocarbon group fuel, in a mixing chamber. The mixed gas is introduced to catalytic reaction chamber via front chamber provided at upstream side of catalytic reaction chamber. The catalytic reaction chamber has catalytic portion (50) containing modification catalyst (C1) rich in low-temperature oxidation activity, and catalyst portion (51) containing modification catalyst (C2) rich in modification activity and provided at downstream side of portion (I). The mixed gas is contacted with a modification catalyst, and hydrogen-containing gas is produced by partial oxidation and water vapor modification. The front chamber is set to temperature, which is more than minimum partial oxidation temperature (T1) and less than self-ignition temperature (T3). The temperature (T3) is temperature, at which gas mixture is self-ignited during period required for mixture to move from mixing chamber to catalytic reaction chamber.    An INDEPENDENT CLAIM is included for manufacturing apparatus of hydrogen-containing gas.    DESCRIPTION OF DRAWING(S) - The figure shows the relationship between inlet port temperature and catalytic reaction room temperature of catalytic chamber. (Drawing includes non-English language text).    Catalytic reaction chamber (5)    Source gas chamber (7)    Mixing chamber (8)    Front chamber (9)    Modification portions (50,51)    Source gas (f1)    Oxygen-containing gas (o)