Gaja-jima belongs to the Tokara Islands, the Northern Ryukyus. It became an uninhabited island after the emigration of the people in July, 1970 out of the island. Fifty-three ant species have been recorded from the Tokara Islands, but no species from Gaja- jima. An expedition to Gaja-jima was carried out by the Kagoshima University Museum from 2011 to 2013, and 30 ant species (20 genera) were collected there. Twenty-one species (16 genera) were newly collected from the island. It should be noted that the famous tramp ant Nylanderia amia (Forel) was not found. The alien tramp ant Technomyrmex brunneus (F. Smith) has been recorded from the Amami Islands, four islands of the Tokara group (Kuchino-shima, Nakano-shima, Akuseki-jima and Takara-jima), Tanega-shima, Yaku-shima, and the Kagoshima mainland, but was absent from Gaja-jima. The larger islands of the Tokara group have been connected to each other and to the Kagoshima Port by Ferry Toshima, but Gaja-jima has never been linked with the other islands of the Tokara group even when it was inhabited by people. Despite the island seems to have a suitable climate for the habitation of T. brunneus, there might have not been any chance for its invasion onto it.