In total 23 species belonging to 14 genera in 4 subfamilies were collected at 6 ports on the Koshiki Islands. The most ant species (14) were collected at Sato Port (Kamikoshiki-shima) and Teuchi Port (Shimokoshiki-shima) respectively. Of the 23 species collected in this study, 5 ant species, Camponotus vitiosus, Nylanderia amia, Paraparatrechina sakurae, Cardiocondyla sp. A and Tetramorium bicarinatum were collected at all of the 6 ports surveyed. In this study, 8 species, Tapinoma melanocephalum, N. amia, C. sp. A, C. obsucurior, P. fervens, P. indica, T. bicarinatum and T. lanuginosum, were alien ant species. Of the 8 alien ant species, N, amia, C. obsucurior and T. lanuginosum were recorded newly in the Koshiki Islands. The dominant ant species measured by the frequency of occurrence at all of the honey baits (180) were Ph. indica (0.41), followed by T. bicarinatum (0.31) and N. amia (0.27). They were attracted to honey baits at all of the 6 ports. The similarity of species composition calculated by Nomura-Simpson’s Coefficient (NSC) was the greatest (0.90) between Taira Port (Nakakoshiki-shima) and Kashima Port (Shimokoshiki-shima), and was the lowest (0.46) between Sato Port and Teuchi Port.