NOVELTY - A nitrogen is adsorbed in an adsorption agent of adsorption towers (A-C) in which adsorption agent for carrying out adsorption separation of nitrogen from gas containing methane is filled. The nitrogen is desorbed from adsorption agent. The adsorption process, regeneration process and pressure restoration process are carried out in parallel by adsorption towers. The recovery process is carried out by recovery process (a) with high-pressure gas and recovery process (b) with low-pressure gas.    USE - Removal of nitrogen in methane gas e.g. coalbed methane, shale gas, livestock-derived biogas and foodstuff residue-derived biogas.    ADVANTAGE - The method enables efficient removal of nitrogen in methane gas.    DETAILED DESCRIPTION - A nitrogen is adsorbed in an adsorption agent of adsorption towers in which adsorption agent for carrying out adsorption separation of nitrogen from gas containing methane as main component is filled under predetermined adsorption pressure. The nitrogen is desorbed from adsorption agent at pressure which is less than the adsorption pressure. The adsorption tower at pressure reduction state is recycled to adsorption pressure. The adsorption process, regeneration process and pressure restoration process are carried out in parallel by adsorption towers such that the nitrogen removal is carried out by switching each process sequentially in each adsorption tower, and the recovery process is carried out by introducing gas discharged from adsorption tower at reduced pressure to adsorption tower under reduced pressure, when transferring to regeneration process from adsorption process. The recovery process is carried out by recovery process (a) with high-pressure gas and recovery process (b) with low-pressure gas. An INDEPENDENT CLAIM is included for nitrogen removal apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of the nitrogen removal apparatus. (Drawing includes non-English language text)    Raw material-supply flow channels (1A-1C)    Air exhaustion paths (2A-2C)    Pressure restoration paths (4A-4C)    Buffer tank (7)    Adsorption towers (A-C)