NOVELTY - Manufacture of methane gas involves using manufacture means including ammonia decomposition catalyst (x) has arranged in an ammonia decomposition chamber (A), and methanation catalyst (y) arranged in a methanation reaction chamber (B), supplying ammonia to ammonia decomposition chamber (A), supplying carbon dioxide and/or carbon monoxide to methanation reaction chamber (B), decomposing ammonia, generating hydrogen, transmitting through hydrogen separation membrane (m), reacting hydrogen, and carbon dioxide and/or carbon monoxide, and producing methane.    USE - Manufacture of methane gas (claimed).    ADVANTAGE - The method economically and efficiently provides methane gas without using hydrogen.    DETAILED DESCRIPTION - Manufacture of methane gas involves using manufacture means including ammonia decomposition catalyst (x) has arranged in an ammonia decomposition chamber (A), and methanation catalyst (y) arranged in a methanation reaction chamber (B), supplying ammonia as a portion of mixed gas to ammonia decomposition chamber (A), supplying carbon dioxide and/or carbon monoxide as a portion of mixed gas to methanation reaction chamber (B), decomposing ammonia by ammonia decomposition catalyst (x) in ammonia decomposition chamber (A), generating hydrogen, transmitting through hydrogen separation membrane (m) to flow into the methanation reaction chamber (B), reacting hydrogen and carbon dioxide and/or carbon monoxide, and producing methane. The ammonia decomposition chamber (A) and methanation reaction chamber (B) are separated by hydrogen separation membrane (m) in the reactor. An INDEPENDENT CLAIM is included for apparatus for manufacturing methane.    DESCRIPTION OF DRAWING(S) - The drawing shows a longitudinal cross-sectional view of the apparatus for manufacturing methane.    Ammonia decomposition chamber (A)    Methanation reaction chamber (B)    Hydrogen separation membrane (m)    Tubular component (p)    Ammonia decomposition catalyst (x)    Coating layer (xC,yC)    Methanation catalyst (y)