Abstract: There is disclosed a method of producing acetals, which comprises reacting a compound of formula (I), at least one compound selected from a group consisting of a compound of formula (II), paraformaldehyde, and trioxane; and a compound of formula (III), to synthesize an acetal of formula (IV), wherein the reaction is carried out in the presence of an oxidizing agent and an acid:  wherein R1 is an alkyl group etc., R2 is an alkyl or aryl group, R3 and R4 each independently are a hydrogen atom, an alkyl group or an aryl group, X1 and X2 each are a group of nonmetal atoms necessary to form a 5- or 6-membered N-containing heteroring, and M is a hydrogen atom or a cation. This method can give acetal compounds with good efficiency and a high yield.