A process of hydrogen production for application to proton exchange membrane fuel cells (PEMFC), a kind of efficient and almost zero-emission power-generation device, was developed by integrating the reactions during the steam reforming of multicomponent liquid hydrocarbon fuels and hydrogen enrichment in a Pd membrane reactor. A highly hydrogen permeable, permselective Pd composite membrane, and an active catalyst for steam reforming of not only higher hydrocarbons but also of methane at temperatures lower than 823 K, made one-step hydrogen production from steam reforming of liquid hydrocarbons in a membrane reactor feasible near practical working conditions. Furthermore, a theoretical energy balance calculation showed that the membrane not only separated hydrogen but also adjusted the selectivities of products, which could be applied to achieve autothermal operation, e. g., catalytic combustion of the reformate from the retentate side of the Pd membrane could provide the energy for the endothermic steam reforming reactions in such a fuel processor system.