An adsorbent is charged into a horizontal type packed column having a multiplicity of packed vessels each of which is composed of a partition plate and a cylindrical body and which are connected through the partition plates, from an opening formed on the upper wall of each cylindrical body. Then, each opening is closed tightly with a detachable plug cover. The partition plate is provided with a first fluid passage through which a fluid is passed in the direction of the axis of the cylindrical body and a second fluid passage which is in communication with the first fluid passage, which extends toward the peripheral wall of the cylindrical body and which opens at the cylindrical body. This apparatus is suitable for use as a multiple-stage adsorption separator directed to a simulated moving-bed system.
