PURPOSE: To efficiently obtain the titled compound in high conversion rate and selectivity, by oxidizing a cycloalkene in the presence of active carbon and an alcohol in the liquid phase using a specific complex type catalyst, terminating the reaction, introducing H2, reducing a Pd catalyst, readily separating and recovering the catalyst.

CONSTITUTION: A cycloalkene, such as cyclopentene, is oxidized in the liquid phase with an oxidizing agent, such as molecular O2, using a Pd compound, such as PdCl2, and at least one compound selected from copper compounds, such as CuCl2, or iron compounds as a catalyst in the presence of active carbon, treated with H2O2, etc., and used as a carrier for the catalyst or in a state of separated from the catalyst and an alcohol. After terminating the reaction, H2 is introduced to reduce the Pd catalyst and the aimed compound useful as an intermediate for high polymers, such as nylon or polyester, plasticizers, etc., is then obtained by separation. Furthermore, expensive Pd can be readily separated and recovered by the coexistence of the active carbon and repeatedly used with hardly any deterioration in catalyst activity.