A diol compound, for example, hexanediol, is produced with a high efficiency by esterifying a carboxylic acid mixture, collected from a reaction product mixture of a liquid phase oxidation of cyclohexane, with an esterifying agent and hydrogenate-decomposing the resultant esterification product mixture with hydrogen. The hydrogenate-decomposition is carried out by using a specific catalyst free from chromium and including a member selected from (A) copper and zinc-containing catalytic materials which are prepared by mixing an aqueous solution of water-soluble copper and zinc salts with an aqueous alkali metal or ammonium carbonate or alkali metal or ammonium hydrogen carbonate solution, reducing the resultant precipitate comprising a basic copper and zinc carbonate mixture with hydrogen and partially oxidizing the resultant reduction product with an oxygen-containing gas, and (B) copper and zinc-containing catalytic materials which are prepared by conducting the same mixing procedure as that for the catalytic material (A) except that the mixing is carried out at a temperature of 60.degree. to 95.degree. C. at a pH of 6.5 to 9.0, and by calcining the resultant precipitate at a temperature of 300.degree. C. to 450.degree. C.