The present invention relates to a catalyst for reforming a hydrocarbon comprising a carrier containing manganese oxide and carried thereon (a) at least one component selected from a ruthenium component, a platinum component, a rhodium component, a palladium component, an iridium component and a nickel component and a process for producing the same and to a process for reforming a hydrocarbon (steam reforming, self thermal reforming, partial oxidation reforming and carbon dioxide reforming) using the above catalyst. Provided are a catalyst for reforming a hydrocarbon which comprises ruthenium, platinum, rhodium, palladium, iridium or nickel as an active component and in which a reforming activity is elevated, a process for producing the same, and a steam reforming process, a self thermal reforming process, a partial oxidation reforming process and a carbon dioxide reforming process for a hydrocarbon using the above catalyst.