In this study, we investigate the antimicrobial and antioxidant activities of extracts of Enteromorpha intestinalis. To evaluate the antimicrobial and antioxidant activities, three solvents (hexane, chloroform and methanol) were applied to obtain extracts. The extraction yields are hexane (A) 1.11%, chloroform (B) 0.94%, and methanol (C) 8.2%. Also, the contents of total phenolic compounds of extract A, B, C are 4.03%, 8.15%, and 2.33%, respectively. In the results of antimicrobial activity, extract A and B have higher activity than that of extract C. Especially, Vibrio vulificus, Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli are more sensitive than others. In antioxidant activity, extract A and B present the higher DPPH activity than that of control (BHA and ascorbic acid). The DPPH radical scavenging activity and SOD-like activity are ordered as B>C>A. However, extract C show high value in ferric reducing antioxidant power assay. In nitrite scavenging activity, extract A is relatively higher than others. However, the antioxidant activities are lower than that of controls (ascorbic acid and BHA). The antioxidant activities are presented the increasing pattern of increasing by the increasing of extract concentration.