NOVELTY - The apparatus (200) has a gas mixing liquid generation unit that generates gas mixing liquid which micro-bubble-ized source gas (G1) into liquid. A melting tank (4) pressurizes gas mixing liquid to dissolve source gas, and to disconnect un-dissolved gas from gas mixing liquid among source gas. The gas mixing liquid generation unit generates micro-bubble when sum total pressure of bubble internal pressure by surface tension of micro-bubble of source gas and liquid pressure pressurized by dissolution desorption unit becomes more than dissolution pressure value.    USE - Gas-purification apparatus such as sewage-gas purifier used for purifying combustible gas e.g. methane gas used in natural gas vehicle, and impurity gas such as carbon dioxide from source gas e.g. sewage gas.    ADVANTAGE - Since the melting tank pressurizes gas mixing liquid to dissolve source gas, and to disconnect un-dissolved gas from gas mixing liquid among source gas, the liquid pressure which pressurizes gas mixing liquid can be made smaller by micro-bubble-izing source gas and utilizing the increase in the bubble internal pressure by the surface tension. The installation cost of the pressure vessel and pump can be reduced and the power consumption of pump can be reduced while reducing running cost so that energy saving can be attained and the economical efficiency of gas-purification apparatuses can be improved. The concentration of combustible gas can be raised so that the purification performance of the combustible gas of sewage-gas purifier can be improved.    DETAILED DESCRIPTION - The apparatus has a volatilization tank (5) that pressure-reduces gas solution generated by dissolution desorption unit to make solution gas dissolve in gas solution foam, and to disconnect solution gas. The solubility of impurity gas is higher than combustible gas. The circulation unit supplies gas mixing liquid and gas volatilization liquid. An un-dissolved gas return unit supplies un-dissolved gas to gas mixing liquid generation unit. An air-purging unit supplies purge air to gas solution. The additional replenishment unit carries out additional replenishment of liquid which is not mixed with remaining gas volatilization liquids after portion is discharged by discharge unit. Ejector (6) sucks source gas with the dynamic pressure of liquid, and generates gas mixing liquid. A pump (2) pumps liquid to ejector. A compressor (3) supplies source gas to ejector. The pump pressurizes gas-liquid two-phase fluid. A nozzle pressure-reduces the liquid mixture pressure-dissolved with pump. A motive power recovery unit e.g. Pelton wheel recovers pressure reductions by pressure reduction of gas solution as motive power, and carries out auxiliary drive of pump. The liquid pressure is less than 0.55 Mpa. The microbubble generation apparatus generates the microbubble which micro-bubble-ized the source gas.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the structure of the sewage-gas purifier. (Drawing includes non-English language text)    Pump (2)    Compressor (3)    Melting tank (4)    Volatilization tank (5)    Ejector (6)    Gas-purification apparatus (200)    Source gas (G1)