Haedae(海帶, haidai) is representative herb from seaweeds, but its origin is still confusing. Thus we analyzed its origin on the basis of classics of oriental medicine. The scientific name of Haedae corresponds to Zostera marina, according to the folkloric use. But, it is Laminaria japonica, according to its habitat, morphological feature, and the korean name on the medical books in Joseon since 17c. In the remote past, it seemed that two groups were segragated by the name of Zostera marina Haedae and Laminaria japonica Haedae. However, it is thought that this two trends were mixed up when medical knowledge was compiled in Song Dynasty era. Documental support inclined to Laminaria japonica, but it is too early to conclude that Laminaria japonica is the Haedae. To prove this hypothesis, further study is required to investige whether Laminaria japonica or Zostera marina has mentioned efficacies of Haedae used for the treatment of wen, San syndromes, edema, scrofula, etc. And we have need of research that solve the origin problem of Gonpo(Laminariae thallus) on the assumption that Laminaria japonica is Haedae.