NOVELTY - A gas-purification apparatus has adsorption tower, product gas collection path, and gas exhaust passage. The gas-purification apparatus further consists of separation membrane which does not allow to-be-purified gas to pass through, and other gases pass, and separates to-be-purified gas from other gases at the exhaust pressure of the adsorption tower, and resurgent-gas collection path for returning resurgent gas, in which the concentration of to-be-purified gas is increased in the separation membrane to the source gas supply path.    USE - Apparatus is used for purifying gas e.g. methane and biogas.    ADVANTAGE - The high purity methane gas is recovered efficiently using gas-purification apparatus.    DETAILED DESCRIPTION - A gas-purification apparatus has adsorption tower filled with adsorbent which adsorbs gases other than to-be-purified gas from source gas, source gas supply path (L1) which supplies source gas to the adsorption tower, product gas collection path (L2) which emits to-be-purified gas which did not adsorb to the adsorbent as product gas, and gas exhaust passage (L3) for desorbing gas which is adsorbed to the adsorbent is exhausted from exhaust passage. The adsorption tower, the source gas supply path, the product gas collection path, and the gas exhaust passage are connected such that the pressure fluctuation operation is performed alternately. The gas-purification apparatus further consists of separation membrane which does not allow to-be-purified gas to pass through, and other gases pass, and separates to-be-purified gas from other gases at the exhaust pressure of the adsorption tower, and resurgent-gas collection path (L5) for returning resurgent gas, in which the concentration of to-be-purified gas is increased in the separation membrane to the source gas supply path.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of gas-purification apparatus. (Drawing includes non-English language text)    Source gas supply path (L1)    Product gas collection path (L2)    Gas exhaust passage (L3)    Product gas cleaning path (L4)    Resurgent gas-return path (L5)    Exhaustion path (L6)