The phytoestrogens including isoflavones (genistein, daidzein, biochanin A, formononetin, and glycitein), coumestrol, and lignans (secoisolariciresinol, matairesinol, and anhydrosecoisolariciresinol) were quantified in edible sea vegetables from Korea. Sea vegetable samples were collected based on domestic consumption data. After hydrolysis of phytoestrogen glycosides in prepared samples, aglycones of phytoestrogens were extracted with diethyl ether and analyzed with isotope dilution gas chromatography-mass spectrometry in selected ion monitoring mode (ID-GC-MS-SIM). Total samples included 19 samples representing eight species. Most of the samples showed rather low concentrations, ranging from not determinated to $79.2;{mu}g/kg$ for isoflavones and from 106.4 to $694.8;{mu}g/kg$ for lignans. The daily intake of phytoestrogen from sea vegetables, estimated from the present data and domestic consumption data, was about $0.13;{mu}g/day$ for isoflavones and $2.0;{mu}g/day$ for lignans. When we compared these results with those from legumes, sea vegetables would not be considered the major source of phytoestrogens in the Korean diet.