Abstract: A process for preparing o-phenylphenol by dehydrogenating at least one of cyclohexanone dimer and o-cyclohexylphenol in the presence of a catalyst, characterized in that the catalyst is one prepared by causing a metal oxide carrier to support at least one compound substantially producing platinum or palladium on the resulting catalyst, at least one compound substantially producing an alkali metal oxide on the resulting catalyst and at least one of hydrogen sulfide, organic sulfur compound and alkali metal sulfide, and heating the carrier at 300.degree. to 400.degree. C.