The invention relates to specific equipment and a specific process by which a diol can be stably produced on a scale of at least one ton per hour over a long period (of 1000 hours or longer). The process comprises feeding a raw material consisting of a cyclic carbonate and an aliphatic monohydric alcohol continuously into a continuous multi-stage distillation column (A) containing a catalyst therein to conduct reactive distillation, withdrawing a low-boiling reaction mixture (AT) containing a formed dialkyl carbonate and the aliphatic monohydric alcohol continuously from the column top in a gas state, withdrawing a high-boiling reaction mixture (AB) containing a formed diol continuously from the column bottom in a liquid state, feeding the high-boiling reaction mixture (AB) continuously into a continuous multi-stage distillation column (C); of specific structure provided with a chimney tray having a liquid receiver and a side-cut withdrawing port set in the receiver, withdrawing continuously substances having lower boiling points than that of the diol as a top cut (CT) and a side cut (Cs), and thus recovering the diol substantially free from substances having boiling points lower than that of the diol as a bottom cut (CB).