Provided is a process for continuously producing xylitol in high yield and productivity using a vacuum microfiltration bioreactor containing a fermentation medium for a strain of the genus Candida, which includes: 5 300 g/l of xylose, 1 10 g/l of urea, 1 10 g/l of potassium diphosphate, 0.01 1 g/l of magnesium sulfate, 0.1-10 mg/l of MnSO.sub.4.4H.sub.2O, 0.1 10 mg/l of CoCl.sub.2.6H.sub.2O, 0.1 10 mg/l of NaMoO.sub.4.2H.sub.2O, 0.1 10 mg/l of ZnSO.sub.4.7H.sub.2O, 0.1 10 mg/l of AlCl.sub.3.6H.sub.2O, 0.1 10 mg/l of CuCl.sub.2.2H.sub.2O, 0.01-5 mg/l of H.sub.3BO.sub.3, 1-100 mg/l of FeSO.sub.4 7H.sub.2O, 0.1-10 mg/l of ascorbic acid, 1-100 mg/l of biotin, 1-100 mg of choline, 1-200 mg/l of folic acid, 1-100 mg/l of inositol, 1-100 mg/l of nicotinic acid, 0.1-10 mg/l of p-aminobezoic acid, 1-100 mg/l of pantothenic acid, 0.1-10 mg/l of pyridoxine, 10-1,000 mg/l of riboflavin, and 1-100 mg/l of thiamine.