PURPOSE: To enable a selective and continuous preparation of aromatic- containing hydrocarbon product by subjecting hydrogen and an olefin-containing hydrocarbon starting material to hydrogenation reaction, then subjecting the resulting product to dehydrocyclodimerization reaction and recovering the obtained aromatic product.

CONSTITUTION: (A) hydrogen and (B) an olefin-containing 2-5C hydrocarbon starting material are passed through a hydrogenation reaction zone having a hydrogenation catalyst and reacted to obtain a hydrogenation reaction zone product flow containing an olefin-based hydrocarbon in an amount of less than 50 mole % or more of that of component (B). Then, at least part of this product flow is passed through a dehydrocyclodimerization reaction zone containing a dehydrocyclodimerization catalyst and reacted to form a dehydrocyclodimerization reaction zone product containing H, methane, ethane, ethylene, a 3-5C aliphatic hydrocarbon, a 6 or more C aliphatic hydrocarbon and an aromatic hydrocarbon and subsequently, this product is recovered.