Three species of the genus Paradoxostoma Fischer, 1855 are reported from the South Korean East Coast: Paradoxostoma flaccidum Schornikov, 1975, P. brunneum Schornikov, 1974, and one new species, P. sokchoensis, new species. The first species was previously reported from the East Sea off the Korean peninsula, with additional Paradoxostoma as part of a species list of an ecological study carried out in South Korea. Paradoxostoma sokchoensis is most closely related to P. depressum Okubo, 1977 and P. assimile Okubo, 1978. Three major differences between the new species and the other two species are: 1) the presence of an unusual group of setulae on the antennule, 2) absence of seta on first segment of L6, and 3) a more slender anterior margin of the carapace.