Purification process for cyclic formals

A purification process for removing water from cyclic formals which comprises the steps of supplying a mixture of a cyclic formal selected from the group consisting of 1,3-dioxolan, 1,4-butanediol formal, diethylene glycol formal, 4-methyl-1,3-dioxolan and 1,3-dioxane, and water into a distillation tower at a supply position, effecting distillation while supplying a hydrophilic solvent (A) selected from the group consisting of 1,4-butanediol monomethyl ether, diethylene glycol monomethyl ether, 1,2-propanediol monomethyl ether, 1,3-propanediol monomethyl ether and dipropylene glycol monomethyl ether having a boiling point from 180.degree. to 250.degree. C. at a position on the tower higher than the mixture, and supplying a purified cyclic formal (X) containing not more than 200 ppm of water into the distillation tower at a position higher than the supply position of the hydrophilic solvent (A), and taking out a purified cyclic formal as a distillate from the top of the tower, and hydrophilic solvent (A) containing water from the bottom of the tower, wherein supplying the purified cyclic formal (X) into the distillation tower at a position higher than the supply position of the hydrophilic solvent (A) prevents migration of hydrophilic solvent (A) and water into the distillate.