Non-dispersive solvent extraction of lactic acid based on anion-exchange reaction with tri-n-octylmethylammonium chloride dissolved in oleyl alcohol, the optimum extraction reagents selected for extractive fermentation of lactic acid with Lactobacillus rhamnosus, was attempted in a microporous hollow fiber membrane device. A satisfactory recovery of lactic acid from both aqueous solution and actual fermented broth was accomplished, signifying the great potential of integrating the membrane extraction with fermentation process. A theoretical model which took into account the mass transfer resistances across organic and aqueous films and membrane was developed to analyze and predict the extraction behavior. The model prediction was found to be in good agreement with the experimentally observed results.