Antioxidants play a putative role in the prevention of diseases and conditions such as heart disease, hypertension, and cancer. Antioxidants are also useful in improving food preservation. Although it is known that beers contain antioxidants, only those found in the pilsner beer have been well studied. In this study, we performed an antioxidant assay by measuring the free radical-scavenging activity of 1, 1-Diphenyl-2-picrylhydrazyl (DPPH) and superoxide-scavenger activity of different styles of beers. The DPPH free radical-scavenging activity was found to be high in beers such as the imperial stout, bock, India Pale Ale (IPA), and stout, with the values being 254.1 (imperial stout), 232.7 (bock), 201.0 (IPA), and 195.8 (stout) nmol Trolox/mℓ. Low-malt beers (including beer-like drinks), Weizenbiers, and pilsner beers showed a low DPPH free radical-scavenging activity, with the values being 54.7 (low-malt beers), 110.9 (Weizenbiers), and 120.9 (pilsner beers) nmol Trolox/mℓ. The superoxide-scavenging activity was found to be high among beers such as imperial stout (90.0%), stout (74.0%), porter (72.5%), and barley wine (71.3%). Blonde ale, pilsner beer, and low-malt beers (including beer-like drinks) showed low superoxide-scavenging activity, with the values being 18.1%, 18.7%, and 19.8%, respectively. The antioxidant activities of some styles of beers such as the imperial stout were lower than those of red wines, but higher than those of white wines. Furthermore, the DPPH free radical-scavenging activity of the beers that we studied showed a high correlation to the total polyphenol content in those beers.