An organic acid is produced by allowing a bacterium belonging to the family Enterobacteriaceae, which has an ability to produce an organic acid and has been modified so that the phosphoenolpyruvate carboxykinase activity is enhanced, and the glucose phosphotransferase activity is decreased, which is selected from Escherichia, Enterobacter, Pantoea, Erwinia, Klebsiella and Raoultella bacteria, or a product obtained by processing the bacterium, to act on an organic raw material in a reaction mixture containing carbonate ions, bicarbonate ions, or carbon dioxide gas to produce the organic acid.