A sample containing a plurality of components to be analyzed is introduced to a separation column at its top through a sample feeding device. The sample thus introduced is separated to the individual components in the separation column. Ion exchange resins capable of undergoing deformation depending upon an applied pressure are filled in the separation column. An eluting solution containing sodium ions is fed to the separation column at its top under a pressure of 40 kg/cm.sup.2 or higher through a feed pump. Components leaving the separation column at its bottom are detected by a detector. After the components have left the separation column, a regenerating solution containing lithium ions is introduced to the separation column at its bottom, and is made to leave the separation column at its top. The ion exchange resins are regenerated by passing the regenerating solution through the separation column, and a separation for another sample is made ready thereby. Another sample is then introduced into the separation column at its bottom and the separated components of the sample are made to leave the separation column at its top.