NOVELTY - A high purity methane gas manufacturing apparatus (101) has decomposition mixing tank (201) and refiner (251). The mixing tank comprises accommodation unit (202) of natural gas hydrate (301), sewage gas intake unit, mixed gas discharge unit to discharge mixed gas produced by mixing sewage gas and natural gas hydrate and decomposition of natural gas hydrate, wastewater unit (I) to discharge water produced by decomposition process, flow path to introduce water from wastewater unit into water storage tank, gas flow path, porous unit and purified gas discharge unit.    USE - High purity methane gas manufacturing apparatus.    ADVANTAGE - The manufacturing apparatus produces high purity methane gas, and traps underwater and carbon dioxide gas in mixed gas efficiently.    DETAILED DESCRIPTION - A high purity methane gas manufacturing apparatus (101) has a sealed decomposition mixing tank (201) and a refiner (251). The mixing tank comprises an accommodation unit (202) of natural gas hydrate (301), sewage gas intake unit to introduce sewage gas obtained by anaerobic treatment of sludge to accommodation unit, a mixed gas discharge unit to discharge mixed gas of produced by mixing sewage gas and natural gas hydrate and decomposition of natural gas hydrate in accommodation unit, a wastewater unit to discharge water produced by decomposition of natural gas hydrate in accommodation unit, a water flow path to introduce water discharged from wastewater unit into a water storage tank, a gas flow path to introduce mixed gas to water storage tank, a porous unit to carry out micro bubbling of mixed gas in water in water storage tank, and is provided in the edge portion of gas flow path, and a purified gas discharge unit to discharge highly purified methane gas from water storage tank. The refiner has a wastewater unit (II) to discharge water stored by water storage tank.    DESCRIPTION OF DRAWING(S) - The drawing shows the conceptual diagram of the high purity methane gas manufacturing apparatus. (Drawing includes non-English text)    High purity methane gas manufacturing apparatus (101)    Sealed decomposition mixing tank (201)    Refiner (251)    Natural gas hydrate (301)    Natural gas hydrate tank (302)