PURPOSE: To obtain the subject compound in high yield, by alkylating benzene or a monoalkylbenzene using a catalyst containing a silica based binder having a prescribed amount or below of alkaline metal content as oxides and crystalline silicate.

CONSTITUTION: Benzene or a monoalkylbenzene is reacted with an alkylating agent to provide a dialkylbenzene. In the process, a catalyst containing a silica based binder with alkaline metal content of ≤0.1wt.% as oxides (e.g., tetraethyl orthosilicate or 'Silicate 40(R)') and a crystalline silicate (especially crystalline silicate of a pentasil type structure having main cavities of oxygen 10-membered rings, such as ZSM5 type zeolite) is used as a catalyst. HIgh raw material conversion rate and high dialkylbenzene selectivity with high yield are obtained by this method. Since catalyst life is extremely long, continuous operation can be carried out in a state of maintained high catalyst activity for a long period.