NOVELTY - To-be-processed gas is supplied from the gas supply side of a column (10) filled with an adsorption agent (20), and gas flowing out of the gas emission side of the column is collected after a passage of preset break-through time. The adsorption material is regenerated by a structure which reduces the pressure inside the column, or a structure which purges the column by the carrier gas. Molecular sieve carbon is used as the adsorption material. A gas having a noble gas except helium gas or an inert gas is used as the carrier gas.    USE - For separating isotope gas.    ADVANTAGE - The method eliminates the use of expensive helium, and provides improved separation efficiency.    DETAILED DESCRIPTION - To-be-processed gas containing gas (I) of atomic or molecular form and gas (II) in which element(s) comprised in gas (I) is replaced with the isotope, is supplied and allowed to pass through with a carrier gas in a column (10) filled with an adsorption material (20). The ratio of concentration of gases (I,II) is then changed. The to-be-processed gas is supplied from the gas supply side of the column, and gas flowing out of the gas emission side of the column is collected after a passage of preset break-through time from the supply start of to-be-processed gas. The adsorption material is regenerated by a structure which reduces the pressure inside the column, or a structure which purges the column by the carrier gas. Molecular sieve carbon is used as the adsorption material. A gas containing a noble gas except helium gas or an inert gas is used as the carrier gas. An INDEPENDENT CLAIM is included for gas-treatment equipment having a column filled with adsorption material, a supplier for to-be-processed gas, a supplier for carrier gas, and a gas collection mechanism connected to the gas emission side of the column.    DESCRIPTION OF DRAWING(S) - The figure shows the conceptual diagram of the gas-treatment equipment.    Column (10)    Adsorption material (20)    Cylinder (30)    Collection cylinder (50)    Mass flow meter (MFC1)