A method for producing a carboxylic acid, characterized in that it comprises reacting an oily solution of an alicyclic alcohol with an aqueous solution of hydrogen peroxide in the presence of a catalyst containing a compound of a metal belonging to Group 6 of the Periodic Table in a heterogeneous solution system. The method allows the production of a carboxylic acid from an alicyclic alcohol in a high yield with good efficiency under mild conditions with easy, simple, and safe operations without the need of a solvent removing operation after the completion of the reaction, and the practice of the method is almost free from the adverse effect or the toxicity on the environment or a human body.