NOVELTY - Source gas from source gas supply path (L1) is introduced into adsorption tower (A1) filled with adsorbent (A11) which adsorbs miscellaneous gases other than methane from methane-containing source gas. While adsorbing miscellaneous gases, the product gas which is not adsorbed by adsorbent is collected in product gas collection path (L2). The obtained miscellaneous gases which are adsorbed by adsorbent are subjected to pressure reduction process and removed through miscellaneous gas exhaust passage (L3). The adsorbed miscellaneous gas is concentrated to obtain methane.    USE - Method for purifying gas e.g. coal-mine gas and biogas.    ADVANTAGE - The method efficiently purifies coal mine gas and biogas, and recovers methane with high purity and reduced energy consumption.    DETAILED DESCRIPTION - Source gas from source gas supply path is introduced into adsorption tower filled with adsorbent which adsorbs miscellaneous gases other than methane from methane-containing source gas. While adsorbing miscellaneous gases, the product gas which is not adsorbed by adsorbent is collected in product gas collection path. The obtained miscellaneous gases which are adsorbed by adsorbent are subjected to pressure reduction process and removed through miscellaneous gas exhaust passage. In the adsorption process, the source gas is contacted for 10-6000 seconds with adsorbent, and the adsorbed miscellaneous gas is concentrated to obtain methane. While using carbon molecular sieve, the adsorbent has pore volume distribution at the time of measuring pore distribution by MP method is 0.38 nm or more of pore diameter. The pore volume in the pore diameter is less than 0.05 cm3/g, and pore volume in 0.34 nm diameter is 0.15 cm3/g or more.    DESCRIPTION OF DRAWING(S) - The drawing shows schematic view of the gas purification apparatus. (Drawing includes non-English language text)    Adsorption towers (A1-A4)    Adsorbents (A11-A41)    Source gas supply path (L1)    Production gas collection path (L2)    Miscellaneous gas exhaust passage (L3)