The Swinhoe's Rail (Coturnicops exquisitus) is the world's smallest, and among the most poorly studied, Rallidae species. While the Japanese archipelago has long been considered a wintering area of this species, vocalizing Swinhoe's Rails have recently been observed during its breeding season in multiple distinct wetlands in northern Japan. During the summer of 2018, we investigated the breeding status of this species at a wetland in the Yufutsu Plain in central Hokkaido, where vocalizing Swinhoe's Rails have been recorded since 2012. To achieve our observations, we combined camera trapping and line-transect surveys with playbacks. Our surveys confirmed the presence of at least 1 family of Swinhoe's Rail and its abandoned nest. We also obtained a previous observation record of a family of this species from local birdwatchers at the Hotokenuma wetland in Aomori Prefecture. This study provides the first breeding evidence of Swinhoe's Rail in Japan, and suggests that this secretive, endangered rail species is a breeding summer visitor to northern Japan.