The present invention provides an industrially advantageous process for producing 5-phenylisophthalic acid, which process attains excellent selectivity and yield and also realizes recovery and reuse of a catalyst.The process for producing 5-phenylisophthalic acid represented by formula (1) is characterized in that the process includes the following steps (A) to (C): (A) reacting m-xylene with cyclohexene in the presence of hydrogen fluoride and boron trifluoride, to thereby produce 1-cyclohexyl-3,5-dimethylbenzene; (B) dehydrogenating the 1-cyclohexyl-3,5-dimethylbenzene produced in step (A) in the presence of a dehydrogenation catalyst, to thereby produce 3,5-dimethylbiphenyl; and (C) dissolving the 3,5-dimethylbiphenyl produced in step (B) in a solvent and oxidizing the 3,5-dimethylbiphenyl in the co-presence of an oxidation catalyst, to thereby produce 5-phenylisophthalic acid.