To produce the subject compound in a high grade in a state reduced in the by-production of the dicarboxylic acids without causing the abnormal operation of the oxidation apparatus by oxidizing an alkyl benzene with molecular oxygen in a liquid phase under a reaction rate controlled to a specific value.

This method for producing the alkylbenzoic acid by oxidizing (A) an alkyl benzene having two or more 1-3C alkyl groups with a molecular oxygen-containing gas in the presence of a soluble heavy metal catalyst. Therein, the characteristic of the method comprises controlling the reaction rate of the component A to ≤25% to convert one alkyl group of the component A into the carboxyl group. For example, the control is performed by operating the oxidation reaction in a boiling and heat-removing state for removing the reaction heat as evaporation heat (e.g. the component A and water are azeotropically boiled, while the water is continuously supplied into an oxidation reactor or while the amount of water discharged from the aqueous phase in the condensed and refluxed liquid of boiling vapors is controlled).