To provide a method for formylating an aromatic compound by which a formylation of an aromatic compound is performed to provide an aromatic aldehydes useful as an intermediate for a dye, a medicine or an agrochemical in high yield and high purity by using bis(trichloromethyl) carbonate and formaldehydes without using harmful phosgene, sulfur or a phosphorus compound.

This method for formylating an aromatic compound comprises a formylation of (A) an aromatic compound {e.g. benzene, naphthalene, pyrrole and isothiazole, each of which may be substituted with a group of an alkyl, an alkoxy, a dialkylamino, an alkylarylamino, etc.} with (B) a complex of bis(trichloromethyl) carbonate (B1) and formamides (B2) such as N,N- dimethylformamide or N-methylformanilide. Moreover, the formylation is preferably performed at 20-150°C, especially 30-100°C.