The Ruddy Kingfisher Halcyon coromanda bangsi breeding in the Ryukyu islands builds its nest in tree holes, termite nests, and various surroundings. We placed artificial nest boxes made from foaming polystyrene on trees in the habitat of the Ruddy Kingfisher. Three of four were dug into and two were used for breeding by kingfishers. Nest building was conducted by both sexes. We report here the nest structure of the artificial nests and the nest construction process of this species.