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A process for producing methylal that involves feeding a liquid containing methanol, formaldehyde and water to an uppermost reactor of at least four solid acid catalyst-filled reactors which are each externally connected to an intermediate portion of a distillation column; and forcibly circulating a liquid containing methanol, formaldehyde, water and produced methylal in a temperature range of 80° C. to 100° C. between the distillation column and each reactor connected to the distillation column below said uppermost reactor, whereby the vapor in the distillation column, which vapor has been subjected to vapor-liquid contact with the liquid containing methanol, formaldehyde, water and produced methylal and which liquid has been subjected to solid-liquid contact in a lowermost reactor of the reactors connected to the intermediate portion of the distillation column, is successively subjected to vapor-liquid contact with the liquids containing methanol, formaldehyde, water and produced methylal circulated between the distillation column and each reactor connected to the distillation column above said lowermost reactor in which the above vapor phase is successively increased.