The ethyl acetate (EtOAc) and chloroform ($CHCl_3$) layers obtained after solvent fractionation of a $H_2O$ suspension of powdered Suaeda japonica juice showed higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity than other layers. Eighteen compounds were purified and isolated from the EtOAc and $CHCl_3$ layers using chromatography following DPPH radical-scavenging assay. These compounds were identified as dihydroferulic acid methyl ester (1), pyrocatechol (2), syringic acid (3), apigenin (4), isorhamnetin (5), kaempferol (6), dihydroferulic acid (7), vanillic acid (8), 4-hydroxybenzoic acid (9), acetophlorglucine (10), homoeriodictyol (11), naringenin (12), quercetin (13), luteolin (14), 9-epi-blumenol C (15), scopoletin (16), dihydroisorhamnetin (17), and chrysoeriol (18). The structures of these compounds were determined by mass spectrometry and nuclear magnetic resonance analyses. The isolated compounds were newly identified from this plant. Compounds 13 and 14 exhibited higher DPPH radical-scavenging activity and an inhibition effect against ferric ion-induced lipid oxidation of rat liver when compared to ${alpha}$-tocopherol and other compounds.