Both sexes of a new species of Miraciidae belonging to the genus Amonardia Lang, 1948 are described. All materials collected from the cultivated brown alga, Undaria pinnatifida of Gijang, Korea. So far only one species, A. normani (Brady, 1872) from the algal bed at Jindo Island was recorded in Korea. The new species can easily be distinguished from its congeners by the combination of characters as follows: (1) shape of first antennular segment in female, (2) setal formular of mandible and maxillule, (3) setae of female sixth leg in female, and (4) shape of P2 endopod and exopod of fifth leg in male.