PURPOSE: To improve adsorption efficiency and cleaning efficiency in an adsorption column loaded with adsorbents by changing the diameter of the adsorption column at intermediate sites along its length so that optimum gas velocity can be achieved depending on the kind of components to be adsorbed and kind of adsorbents, etc.

CONSTITUTION: In an adsorption column 30 loaded with adsorbents, the diameter thereof is changed intermediate along its length. As a result, the gas velocity within the column can be varied, enabling the separation efficiency of a strong adsorption component to be changed. Particularly in a pressure-variable adsorption-separation device, by enlarging partially the column diameter D2 on the side of cleaning gas outlet, the gas velocity on the outlet side can be decreased, with the result that cleaning efficiency is improved and quantity of gas for cleaning is deceased, leading to improved yield of products.