ABSTRACT This paper attempts to reveal the biogeographic characteristics of ant fauna of the islands among Korean South Sea, using quantitative analyses. The data treated in this paper are those from Cheongsando Is. and 10 other islands in South Sea which have been well investigated. The faunal similarity is examined using the Nomura‐Simpson's Coefficient (NSC). Futhermore, the obtained NSC value matrix is examined by a cluster analysis using UPGMA method. The number of species which has been recorded in the 11 islands are 91 species belonging to 34 genera under 4 subfamilies. Among the above 11 islands, Jejudo Is., which is the largest, has the highest number of species, 67 spp., while Geogeumdo Is. has the lowest, 21 spp. Cheongsando Is. which has directly been investigated by authors has 30 species. The NSC‐ values between the 11 localities investigated range from 0.522 (Wando Is. to Saryangdo Is.) to 1.000 (Namhaedo Is. to Geojedo Is.). The comparative NSC value of Cheongsando Is. and 10 islands range from 0.522 (to Saryangdo Is.) to 0.833 (to Jejudo Is). The cluster analysis using a similarity index (NSC) showed that the islands of these areas could be grouped into 3, a level of 32%. The similarity of Soando Is. and Geomundo Is. were the closest, 63%, while Soando Is. and Namhaedo Is. were the remotest, 32%. The similarity of Jindo Is. and Cheongsando Is, was 63%, while that of Namhaedo Is. and Cheongsando Is. was 32%.