NOVELTY - A hydrogen-producing catalyst comprises a catalyst component layer formed by volume coating 200-500 g catalyst component per 1 liter of honeycomb molded product, on honeycomb molded product having a polygonal cell. The average thickness of catalyst component layer in the portion of the edge length which is quarter to the left and right from the center of the cell edge, is 10-60 mu m. The apparent density of catalyst component is 1.3-4 g/mL.    USE - Catalyst is used for producing hydrogen (claimed) for hydrogen source for fuel cells and chemical reactions.    ADVANTAGE - The hydrogen-producing catalyst enables effective decomposition of ammonia with high line speed and produces hydrogen with high yield.    DETAILED DESCRIPTION - A hydrogen-producing catalyst comprises a catalyst component layer formed by volume coating 200-500 g catalyst component per 1 liter of honeycomb molded product, on honeycomb molded product having a polygonal cell. The average thickness of catalyst component layer in the portion of the edge length which is quarter to the left and right from the center of the cell edge, is 10-60 mu m. The apparent density of catalyst component is 1.3-4 g/mL, as measured using the relation: ( rho )=1/(Vp+(1/( rho )t)), where ( rho ) is apparent density in g/mL, Vp is pore volume in mL/g, ( rho )t is true density in g/mL and obtained from mercury intrusion technique. INDEPENDENT CLAIMS are included for the following:    (1) manufacture of hydrogen-producing catalyst, which involves preparing aqueous slurry containing catalyst component having secondary particle diameter of 10 mu m or more and number fraction of particles 0% or less, and catalyst component particles having average particle diameter of 5 mu m or less, coating aqueous slurry on a ceramic compact, drying and/or baking; and    (2) production of hydrogen, which involves decomposing ammonia using catalyst.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of catalyst coating in a honeycomb cell. (Drawing includes non-English language text)