PURPOSE: To accelerate the reaction by using a ruthenium-contg. catalyst at the time of migrating a halogen from a polyhalogenated arom. compd. to a monohalogenated or nonhalogenated arom. compd.

CONSTITUTION: (A) The polyhalogenated arom. compd. and (B) the monohalogenated or nonhalogenated arom. compd. are brought into reaction in the presence of the catalyst contg. (C) the ruthenium in the form of an element or compd. and if desired, further, contg. (D) ≥1 kinds of the metals (for example, copper, silver, gold, zinc, mercury or cadmium) of groups I and II of periodic table or their compds. and more particularly the salts of the copper and silver, by which the halogen is migrated from A to B. The component C in the catalyst exhibits good activity at the time of the migration of the halogen from A to B and the addition of the component D greatly improves its activity.