To provide a method for producing natural aromatic, aliphatic and thio-carboxylic acids by fermentation, which is a biological method for producing various kinds of carboxylic acids by an enzymic oxidation of corresponding alcohols by using an alcohol oxidase in very high yield.

This method for producing the aromatic, aliphatic and thio- carboxylic acids comprises using a cultured product containing bacteria belonging to the genus Gluconobacter.