TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Apparatus: The gas-manufacturing apparatus further has hydrogen gas manufacture unit capable of manufacturing hydrogen gas using water mixture as raw material. Preferred Condition: The methane gas manufacture unit generates methane gas in reactor (A) at 300 plus minus 150 degrees C. The hydrogen gas manufacture unit generates hydrogen gas in reactor (B) at 700 plus minus 150 degrees C. The reactor (A) and reactor (B) are connected, and heat generated in the reactor (A) is supplied to the reactor (B).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: Liquid other than water is oil, dimethyl ether, alcohol, tar, hydrocarbon-type liquid, and benzene, toluene and/or xylene, preferably oil and alcohol. The alcohol is ethanol or methanol. The oil contains naphtha, gasoline, kerosene oil, light oil, A heavy oil, B fuel oil, C heavy oil, crude oil, vegetable oil including algae oil, animal oil and/or waste oil. The vegetable oil is tempura waste oil. Water contains catalyst. The catalyst is potassium carbonate. The addition amount of potassium carbonate differs depending on the hardness. Preferred Process: Reaction of dimethyl ether and water to yield carbon dioxide, methane, two molecules of hydrogen, and 411.3 MJ/kmol of heat, reaction of ethanol and water to yield carbon dioxide, methane, two molecules of hydrogen and 411.3 MJ/kmol of heat, reaction of pentane, two molecules of water, and methanol to yield carbon dioxide, carbon monoxide, four molecules of methane, 2 molecules of hydrogen, and 689.4 MJ/kmol of heat, reaction of pentane, two molecules of water, and ethanol to yield carbon dioxide, carbon monoxide, five molecules of methane, hydrogen, and 764.3 MJ/kmol of heat, and reaction of linoleic acid and nine molecules of water to yield 5.5 molecules of carbon dioxide and 12.5 molecules of methane, are carried out in methane gas manufacture unit. Reaction of dimethyl ether and 2 molecules of water to yield carbon dioxide, carbon monoxide, and 411.3 MJ/kmol of heat, reaction of methanol and water to yield carbon dioxide, 3 molecules of hydrogen, and 336.4 MJ/kmol of heat, reaction of ethanol and 2 molecules of water to yield carbon dioxide, carbon monoxide, 5 molecules of hydrogen, and 447 MJ/kmol of heat, reaction of pentane, 6 molecules of water, and methanol to yield carbon dioxide, 5 molecules of carbon monoxide, 14 molecules of hydrogen, and 492.3 MJ/kmol of heat, and reaction of pentane, 7 molecules of water, and ethanol to yield carbon dioxide, 6 molecules of carbon monoxide, 16 molecules of hydrogen and 656.8 MJ/kmol of heat, are carried out in hydrogen gas manufacture unit.