TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: In the catalyst structure, the metal monolith is a honeycomb made of a metal having durability at high temperature, and has a cell density of 50 - 1000 cells/in2. The nickel-based steam reforming catalyst contains nickel, alumina and basic solids. In the structure, the applied amount of the nickel-based steam reforming catalyst is 0.01 - 0.4 g/cc of the metal monolith. Preferred Process: The mixed gas of hydrocarbon and steam has a space velocity of 1000 - 50000 hr-1. The molar ratio of the steam to the hydrocarbon is 1 - 5 moles per mole of carbon of hydrocarbon. EXAMPLE - A metal monolith was prepared by using an iron-chromium-aluminum alloy (fecralloy) plate (having density of cells of 640 cells/in2) and was preoxidized. A catalyst (containing nickel (10%) and alumina (balance) and alkaline compounds used as a commercial steam reforming process was finely powdered and mixed with water to prepare slurry. To the slurry, nitric acid was added. The metal monolith was coated by immersion in the slurry, and then sintered at 900degreesC to give a metal monolith catalyst (test) having a washcoat with the nickel-based catalyst applied on it. The washcoat amount of the catalyst prepared was 0.22 g per cc of the monolith. For comparison a nickel-based pellet catalyst used in a commercial steam reforming process was crushed, and sieved through a sieve of 4 - 10 mesh to give catalyst pellets (control) with an average diameter of 3 mm. The metal monolith catalyst (3.2 g of a nickel-based catalyst) having a diameter of 2.1 cm and a height of 2 cm was loaded in a quartz reactor having an inner diameter of 2.1 cm, and a methane steam reforming reaction was performed in the reactor at catalyst temperature of 731degreesC. The nickel based steam reforming catalyst pellets having diameter of 3 mm was loaded in a quartz reactor having an inner diameter of 2.1 cm and height of 4 cm and a methane steam reforming reaction was performed in the reactor at catalyst temperature of 783degreesC. In the methane steam reforming reaction test, the space velocity of reaction gas was 9440 hr-1 and was obtained by dividing the flow rate of reaction gas at 20degreesC and atmospheric pressure by the volume of the catalyst. The reaction gas used in the reaction was a mixed gas of methane and steam, in which the ratio of steam to methane was 3 (in case of test). The reactor was heated by an external heating furnace and the methane steam reforming performance of the catalysts was analyzed. The activity of the catalyst filled in each of the reactors was tested at space velocity of 9440 hr-1 and methane conversion was calculated. The methane conversion (%) for test/control was found to be 99/97.9.