To improve the activity of a catalyst by preparing the catalyst to be used in the production of an acyl group substituted aromatic compound by reacting an aromatic compound with a carboxylic acid or its derivative by incorporating zeolite and graphite.

In the production of an acyl group substituted aromatic compound, when an aromatic compound is reacted with a carboxylic acid or its derivative, contact with a catalyst containing zeolite and graphite is made. The catalyst is prepared preferably by molding zeolite with graphite. The type of zeolite to be used is preferably selected from a beta type, a pentasyl type, a faujasite type, and others. As regards the aromatic compound, an aromatic hydrocarbon, an aromatic ether compound, and others are named. The amount of a spent zeolite catalyst to be used in batch operation or semi-batch operation and others, is made 0.1-100 wt.% to the total amount of an organic reactant to be reacted.