PURPOSE: To safely obtain the subject compd. with ease of temp. control during reaction and with decreased side products by subjecting cyclohexanone or cyclohexanol or a mixture composed thereof to nitric acid oxidation by using an acetic acid solvent in the presence a catalyst.

CONSTITUTION: The objective compd. is obtd. by bringing the cyclohexanone or the cyclohexanol alone or the mixture composed of the cyclohexanone and the cyclohexanol as a raw material into reaction at 45 to 90°C, more preferably 50 to 80°C under a reaction pressure regulated to 1 to 3 atm by using an ammonium, nitrate or acetate salt of vanadium, copper, cobalt, manganese, etc., as the catalyst in the acetic acid solvent. The amt. of the catalyst to be used is preferably in a range of 0.005 to 0.05 parts for each 1 part of the raw materials in the case of the vanadium salt and 0.001 to 0.05 parts in the case of the cobalt and manganese salts. The ratio of the acetic acid solvent is preferably about 0.1 to 25 parts for each one part of the raw material oil.