The process for preparing 5-deoxy-arabinose comprises reacting 5-tosyl-L-arabinose-dialkylmercaptal with NaBH4 in DMSO to give 5-deoxy-L-arabinose-dialkyl-mercaptal and then reacting the obtained 5-deoxy-L-arabinose-dialkyl- mercaptal with hydrochloric acid in DMSO. According to the process, 5-deoxy-L-arabinose can be obtained in a high yield without employing heavy metal such as mercury.