A natural-gas purification apparatus includes: a compressor that adjusts the pressure of natural gas; a cooling unit that liquefies and separates a part of natural-gas liquid by cooling the natural gas after the pressure adjustment by the compressor; a heating unit that heats the natural gas after the separation of the part of the natural-gas liquid by the cooling unit; carbon-dioxide separation units that are arranged in series and separate carbon dioxide from the natural gas heated by the heating unit through carbon-dioxide separation membranes; and a thermostatic chamber that adjusts the temperature of at least the carbon-dioxide separation unit disposed at the most downstream side among the carbon-dioxide separation units.
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