Some hydromedusae were collected from Gijang (Busan), Yeounggwang, Munseom (Jejudo Is.) and Shinhangman with Issacc-Kidd Midwater trawl net or by SCUBA diving from 2001 to 2003. They were identified into five species of five families in three orders and are new to the Korean fauna. Bougainvillia ramosa (van Benenden, 1844) of the family Bougainvilliidae in the order Anthomedusae, Phialidium hemishaericum (Linne, 1767) of the family Campanulariidae and Aeguorea macrodactyla of the family Aequoreidae in the order Leptomedusae, Diphyes dispar (Chamisso and Eysenhardt, 1821) of the family Diphydae and Abylopsis tetragona (Otto, 1823) of the family Abylidae in the order Siphonophora. With a result of this work, the Korean hydromedusa fauna consists of 31 species of 18 families in six orders.