A process of manufacturing optically active (S)-1,2-diols, wherein (R)-1,2-diols represented by the general formula [I] ##STR1## (where: R represents a substituted or unsubstituted alkyl group, alkenyl group, aryl group or aralkyl group) or a mixture of diols of the general formula [I] and (S)-1,2-diols represented by the general formula [II] ##STR2## (Where: R represents the same as above) having an opposite configuration to the general formula [I] is subjected to the action of a microorganism capable of selectively metabolizing the diols of the general formula [I], or capable of converting the diols of the general formula [I] into the diols of the general formula [II], or having the both capabilities, and the formed and accumulated (S)-1,2-diols of the general formula [II] is collected. According to the present invention, optically active (S)-1,2-diols can be produced commercially and advantageously.