A process for increasing the production of light olefin hydrocarbons from a hydrocarbon feedstock. A process for producing an aromatic hydrocarbon mixture and liquefied petroleum gas (LPG) from a hydrocarbon mixture, and a process for producing a hydrocarbon feedstock which is capable of being used as a feedstock in the former process, that is to say, a fluidized catalytic cracking (FCC) process, a catalytic reforming process, and/or a pyrolysis process, are integrated, thereby it is possible to increase the production of C.sub.2-C.sub.4 light olefin hydrocarbons.