Spotted seahorses, Hippocampus kuda , were separated into two portions: belly and rest body portion. Antioxidative activity of hot-water and ethanol extract of Hippocampus kuda seahorse was evaluated using four different methods, including DPPH free radicals scavenging activity, SOD-like activity, reducing power and Fe+2 chelating activity, and immune activity was assessed by using HB4C5 and J774.1 cells. It was found that the antioxidative activities of belly extract were higher than the extract from the rest body portion, but the Fe+2 chelating activities were all lower than 9%. The HB4C5 cells showed the maximum relative activities of cell proliferation (155%) and IgM secretion (140%) at 350 μg/ml of hot-water belly extract. The ethanol belly extract at 130 μg/ml under could stimulate cell proliferation (142%) and IgM secretion (130%). At 700 μg/ml, the extract showed the maximum relative activities of cell proliferation (148%) of J774.1 cells.