NOVELTY - A hydrocarbon group fuel and water vapor are reacted in a reactor (2) to produce hydrogen and carbon dioxide. The ionization of oxygen existing on the outer side of the reactor is carried, and oxygen ion is moved via an oxygen ion conductor. The oxygen ion is then electrochemically reacted with hydrogen or with the hydrocarbon group fuel, and water and heat are supplied to the reactor.    USE - For manufacturing hydrogen useful as fuel for fuel cells of electric vehicles.    ADVANTAGE - The high-efficiency manufacturing method enables efficient supply of water and heat to the reactor. Water and heat are maintained in a closed cycle, and energy efficiency of hydrogen manufacturing apparatus is improved. Since the fuel cell is a single cell, the need for an interconnector is eliminated. Thus, mass-production of fuel cell without an interconnector is enabled economically.    DETAILED DESCRIPTION - A hydrocarbon group fuel and water vapor are reacted to produce hydrogen and carbon dioxide, in a reactor comprising electrode (I) arranged at the outer side. Electrode (II) is arranged in a circuit connected to the reactor, or in the reactor. The electrodes are connected by an oxygen ion conductor. The ionization of oxygen existing on the outer side of the reactor is carried out by electrode (I), and oxygen ion is moved via the oxygen ion conductor. The oxygen ion in electrode (II) is then electrochemically reacted with hydrogen or with the hydrocarbon group fuel in the reactor, and water and heat are supplied to the reactor.    An INDEPENDENT CLAIM is included for high-efficiency hydrogen manufacturing apparatus (1) having electrode (I), an oxygen ion conductor, and a hydrothermal supplier (7) equipped with electrode (II). The hydrothermal supplier supplies water and heat to the reactor.    DESCRIPTION OF DRAWING(S) - The figure shows the outline block diagram of the high-efficiency hydrogen manufacturing apparatus. (Drawing includes non-English language text).    high-efficiency hydrogen manufacturing apparatus (1)    reactor (2)    hydrogen separation chamber (4)    hydrothermal supplier (7)    fuel cell (13)