Super Ohtaka, a fermented beverage of plant extracts, is prepared from approximately 50 kinds of fruits and vegetables. Natural fermentation is mainly performed by lactic acid bacteria ( spp.) and yeast ( spp.). Four water-soluble polysaccharide fractions were obtained from Super Ohtaka by dialysis, ion exchange chromatography, and gel filtration chromatography; these fractions were designated as OEP1-1, OEP1-2, OEP2, and OEP3. OEP1-1 is a polysaccharide composed solely of glucose. The other fractions contained polysaccharides composed of glucose, galactose, mannose, and a small amount of arabinose. OEP2 and OEP3 contained phosphorus, which was not detected in OEP1-1 and OEP1-2. Furthermore, the immunomodulatory activity of the polysaccharides was investigated in murine macrophage cell lines. OEP2 and OEP3 significantly induced nitric oxide (NO) secretion by macrophages in a dose-dependent manner (concentration range of 4 to 100 µg/mL). When the concentration of OEP3 was 100 µg/mL, NO production was almost identical to lipopolysaccharide (LPS; 10 ng/mL) used as a positive control. Notably, OEP3 induced NO secretion more strongly than OEP2. This trend was also observed for TNF-α, IL-1β, IL-6, and IL-12 p40 secretion. Overall, our studies on polysaccharides isolated from Super Ohtaka suggest that the fermented beverage stimulates macrophages and activates the immune system.