NOVELTY - Producing a substitute natural gas, comprises generating carbon monoxide and hydrogen using coal and a metal fuel, and generating methane from the generated carbon monoxide and hydrogen.    USE - The method is useful for producing a substitute natural gas (claimed) which is useful for power generation, industrial use, and domestic use.    ADVANTAGE - The method: replaces part of coal with a metal fuel, thus the amount of used coal (which generates a lot of carbon dioxide) is reduced, and reduces environmental pollution; requires less energy to perform gasification than that when only coal is used, due to generation of hydrogen from a metal fuel which is an exothermic reaction; performs methanation smoothly even by using a single gasification unit, when the method performs a reaction for removing an oxide film generated on a surface of a metal fuel; and reduces the time taken to perform gas cleaning.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for an substitute natural gas producing device comprising either: a first gasification unit (110) which generates carbon monoxide and primary hydrogen using coal and a metal fuel, a second gasification unit (120) which generates secondary hydrogen using a metal fuel, a gas cleaning unit (200) which removes impurities from the generated carbon monoxide and hydrogen, and a methanation unit (300) which generates the substitute natural gas from the generated carbon monoxide and primary and secondary hydrogen, where the second gasification unit supplies the generated secondary hydrogen to the first gasification unit; or a gasification unit which generates carbon monoxide and hydrogen using coal and a metal fuel, the gas cleaning unit, and the methanation unit, where the gasification unit is configured to intake alkaline material.    DESCRIPTION OF DRAWING(S) - The figure shows a block diagram of producing the substitute natural gas.    First gasification unit (110)    Second gasification unit (120)    Gas cleaning unit (200)    Methanation unit (300)