A process for chlorination of methylated aromatic compounds in a titanium tetrachloride is disclosed. The ring chlorination is first carried out by reacting said methylated aromatic compounds with chlorine gas under reduced light conditions, and then the side chain chlorination is carried out by reacting the resulting mixture with chlorine gas under light irradiation conditions. The process ensures continuous chlorination of aromatic rings and side chains of methylated aromatic compounds at a high yield without using any catalysts or perilous solvents such as carbon tetrachloride.