A catalyst for alkylation contains an inorganic structural material having an ion-exchange ability and a metal ion having a valency of 2 or more. The metal ion is supported on the inorganic structural material. The inorganic structural material is preferably a zeolite. The metal ion is preferably a lanthanide metal. The catalyst for alkylation imparts industrially satisfiable activity and selectivity and can be readily separated, collected and recycled. Furthermore, the process for producing an alkylaromatic hydrocarbon compound includes reacting an aromatic hydrocarbon compound and a compound having an unsaturated bond in the presence of the catalyst for alkylation.