An object of the present invention is to provide is to a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, to provide a specific apparatus and method for producing high-purity diol on an industrial scale. And by the, for example, a high purity diol 1 ton or more per hour, preferably 2 tons or more, more preferably in an amount of 3 tons or more, long-term (e.g., 1000 hours or more, preferably 3000 hours or more, more preferably to provide a specific inexpensive industrial apparatus and industrial production process for producing more than 5000 hours) in a stable manner. According to the present invention, the continuous multi-stage distillation column A having a specific structure, using a continuous multi-stage distillation column C and the continuous multi-stage distillation column E, yet having a specific structure installed in the enrichment section of said continuous multi-stage distillation column E from a side cut outlet installed in the lower portion of the chimney tray, by extracting the components of the liquid, the above problems can be achieved.