A process for separating an organic acid or acids from an organic acid-containing solution obtained by a fermentation method in which glucose is used as starting material, which comprises contacting said organic acid-containing solution to a cation exchange resin to have the organic acid or acids adsorbed on the cation exchange resin, then contacting the cation exchange resin to an eluent to have the organic acid or acids desorbed, and then separating from the eluate a solution containing the organic acid or acids, wherein said organic acid-containing solution is contacted to the cation exchange resin under such a condition that the pH or the organic acid-containing solution is maintained at a pH level lower than pKa where Ka is the ionization constant of the organic acid or acids or the primary ionization constant in a case of a polybasic acid or acids, and the pH of the eluate is maintained at the above pH level.