TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Arrangement: The CO oxidation unit, modification reaction unit and evaporation unit are formed in a container (1). The heat supply unit is contained in an air tight container (4). At least part of the space between the containers (1,4) is made into combustion gas flow path. The combustion gas flow path comprises a honeycomb shaped ceramic or metal surface contacting with the container (1) main body. A catalyst for combustion (16b) is contained on the honeycomb surface. The modification reaction unit or CO oxidation unit has a metal or ceramic honeycomb shaped gas passageway and the catalyst for combustion or modification is provided over the honeycomb surface. The gas passageway of the modification reaction unit is made such that the inner side of the same flat surface or the lamination direction makes a return flow. The catalyst for combustion is provided between the catalyst for modification and the fuel supply port for modification. Upstream of the modification reaction unit is equipped with a catalyst for combustion and a fuel supply port (25) for modification of modification reaction unit. The fuel supply ports for combustion and combustion air supply port are arranged in the upstream along the combustion gas flow path formed in the space between the containers. The catalysts for combustion are respectively provided in the downstream of each fuel supply port for combustion. The evaporation unit is arranged in the combustion zone of the second catalyst for combustion. Fuel (1) is injected in the combustion gas flow path from the fuel supply port through a nozzle. A piping for supply and exhaust of container (4) is provided in the side of container (4). The evaporation unit is spirally formed using a flexible pipe or a bellows pipe. A heat transfer fin is provided in the pipe outer surface. A heat insulating material (38) such as a blanket is arranged in the inner surface of container (4). A plate fin type heat exchanger (37) for pre-heating the fuel for modification is provided in the combustion gas flow path downstream side of modification reaction unit.Preferred Composition: Containers (1,4) contain a lid which plugs up the box shaped main body and the box-shaped opening having an upper openable part.Preferred Process: Combustion air is supplied to the space between the containers from the combustion air supply port to reach the catalyst for combustion after flowing along one main surface of the container containing the CO oxidation unit. Fuel (1) is supplied to fuel supply port (20a) for combustion and fuel (2) is supplied to the fuel supply port (20b) for combustion.