To provide a method for producing a cycloalkanol and/or a cycloalkanone by oxidizing a cycloalkane at a high conversion ratio.

The method is one for producing a cycloalkanol and/or a cycloalkanone by oxidizing a cycloalkane with an oxygen-containing gas in a reaction vessel, wherein the cycloalkanol and/or the cycloalkanone are produced by feeding the oxygen-containing gas and a liquid into a bubble generator to generate a bubble-containing gas/liquid mixture and feeding the gas/liquid mixture into the liquid phase in the reaction vessel. It is desirable that the bubble generator is an ejector-type bubble generator.