To determine the seasonal variation of bacterial community in the seawater of Gwangyang Bay, three hundred thirty six bacterial strains were isolated on February, May, July and October 2011. Amplified Ribosomal DNA Restriction Analysis (ARDRA) was used to construct the phylotyes of the isolates using the restriction endonuclease, Hae III. Diversity indices of ARDRA patterns were calculated. One hundred and one phylotypes including 40 unique pylotypes were found at the 80% similarity level. Partial 16S rRNA genes of one hundred thirty nine strains representing each phylotypes were sequenced and compared. Bacterial community composed of 4 different phyla which include Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes. Proteobacteria was the prevailing phylum in all seasons, followed by Bacteroidetes in winter, spring and autumn while Actinobacteria in summer. At the family level, Flavobacteriaceae dominated in winter and spring and Pseudoalteromonadaceae did in summer and autumn. Genera Altererythrobacter, Loktanella, Pseudoalteromonas and Vibrio were encountered in all seasons. The most diverse bacterial community was found in autumn followed by the order of spring, winter and summer.