We have developed a novel method to separate metallic and semiconducting single-wall carbon nanotubes (SWCNTs) with high purities using agarose gel column chromatography. The synthesis of SWCNTs usually yields a 1:2 mixture of metallic and semiconducting SWCNTs. Although these two types of SWCNTs must be separated for their application in electronic devices, this separation could not be achieved easily. The developed method uses a column filled with agarose gel beads, in which the semiconducting SWCNTs are selectively adsorbed and then eluted. The column can be used repeatedly, and the separation process can be easily automated. Purities of separation were 95 and 90 % for semiconducting and metallic SWCNTs, respectively. Because this continuous, repeatable separation method is applicable to a low-cost, large-scale process, it should enable the industrial production of metallic and semiconducting SWCNTs.