Cyanobacteria produce industrially important secondary metabolites such as lipopeptide, oligosaccharide, fatty acid (esp. sulfolipid), etc. Among them, Synechocystis PCC6803 is the first strain with a publicly available full genome sequence, as of 1996, and is one of the most extensively studied photosynthetic microorganisms. Using this genomic information, the central metabolism of Synechocystis PCC6803 was reconstructed, including photosynthesis, oxidative phosphorylation, glycolysis, pyruvate metabolism, TCA cycle, carbon fixation, and transport system. Each biochemical reaction was carefully incorporated into the model, taking into consideration the metabolite formula, stoichiometry, charge balance, and thermodynamic properties using information from genomic and metabolic databases as well as biochemical literature. The metabolic flux of the model was calculated using flux balance analysis according to its cultivation with various carbon sources. The results of simulation were in accordance with experimental data, which suggests that the central metabolism model can properly estimate the behavior of Synechocystis PCC6803. This model would aid in the understanding of the whole cell metabolism of Synechocystis PCC6803, the first effort of its kind for photosynthetic bacteria.