NOVELTY - The method for producing hydrogen on board of a vehicle equipped with a combustion engine, comprises producing the hydrogen by dehydrogenation of hydrocarbon fuel supplied from a fuel reservoir (12) for the combustion engine and a reactor (20), where the hydrocarbon-fuel supplied to the reactor is provided as fractions, which are produced through fractionation (16) of a fuel removed from the fuel reservoir. The fractionation has a distillative fractionation and fractionation by a semi-permeable membrane and cooling.    USE - The method is useful for producing hydrogen on board of a vehicle equipped with a combustion engine.    ADVANTAGE - The method is capable of producing hydrogen with high purity, to achieve a high reaction yield and reaction rate, and to improve performance properties on board of a vehicle equipped with a combustion engine.    DETAILED DESCRIPTION - The method for producing hydrogen on board of a vehicle equipped with a combustion engine, comprises producing the hydrogen by dehydrogenation of hydrocarbon fuel supplied from a fuel reservoir (12) for the combustion engine and a reactor (20), where the hydrocarbon-fuel supplied to the reactor is provided as fractions, which are produced through fractionation (16) of a fuel removed from the fuel reservoir. The fractionation has a distillative fractionation and fractionation by a semi-permeable membrane and cooling. The fuel reservoir is provided for the combustion engine operated with kerosene and the fraction of the kerosene provided as hydrocarbon-fuel for the reactor. The dehydrogenation is allowed to proceed with a reaction temperature of less than 400 degrees C. One of the fuels produced by the fractionation and the fraction supplied to the reactor is not returned to the fuel reservoir. An INDEPENDENT CLAIM is included for a device for producing hydrogen on board of a vehicle equipped with a combustion engine.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a device for producing hydrogen on board of a vehicle equipped with a combustion engine.    Fuel reservoir (12)    First fuel supply (14)    Fractionation (16)    Second fuel supply (18)    Reactor. (20)