NOVELTY - The natural gas reformer consists of primary modifier which modifies natural gas containing methane (CH4), into carbon and hydrogen (H), and secondary modifier to react carbon dioxide (CO2) and carbon to form carbon monoxide (CO). CH4 and CO2 inlets are respectively connected to primary and secondary modifiers. H and CO outlets are respectively connected to primary and secondary modifiers.    USE - For modifying natural gas into hydrogen and carbon monoxide which are used as fuel for fuel cell, engine and motor vehicle.    ADVANTAGE - Modification of methane and carbon dioxide are carried out alternately. Thus, carbon monoxide and hydrogen are obtained separately and continuously. The heat of combustion exhaust gas ejected from combustor is effectively used as heat source of modifier. The hydrogen ejected from the modifier is effectively used by the fuel cell. The modified natural gas is effectively used as fuel for motor vehicles, which is a substitute of petroleum group fuel. Thus, the efficiency of motor vehicle is improved.    DETAILED DESCRIPTION - The natural gas reformer consists of a primary modifier which modifies natural gas containing CH4, into carbon and H. Secondary modifier is provided to react CO2 and carbon, to form CO. CH4 and CO2 inlets are respectively connected to primary and secondary modifiers. H and CO outlets are respectively connected to primary and secondary modifiers. Each inlets and outlets are equipped with valve for controlling flow of gas. INDEPENDENT CLAIMS are included for the following:    (1) Natural gas hybrid system comprises a fuel cell (4) connected to the hydrogen outlet of modifier (1), combustor (3) connected to carbon monoxide outlet of modifier, CO2 separator (5) for separating CO2 from combustion exhaust gas generated within the combustor; and    (2) Natural gas modification method involves contacting natural gas containing methane with a methane modification catalyst to modify methane into carbon and hydrogen, and subsequently contacting modification catalyst with carbon dioxide such that carbon dioxide reacts with carbon which is previously absorbed in the catalyst to form carbon monoxide.    DESCRIPTION OF DRAWING(S) - The figure shows the block diagram of natural gas hybrid system. (Drawing includes non-English language text).    modifier (1)    combustor (3)    fuel cell (4)    carbon dioxide separator (5)