In connection with the process for producing a highly purified aromatic dicarboxylic acid through liquid-phase oxidation of an alkylated aromatic hydrocarbon by means of an oxygen-containing gas in the presence of a catalyst composed of Co, Mn and Br to thereby obtain a crude aromatic dicarboxylic acid and subsequent hydrogenation purification of the crude aromatic dicarboxylic acid in the form ofan aqueous solution, it is intended to provide economic production of a crude aromatic dicarboxylic acid to be fed to hydrogenation purification in which aromatic monocarboxylic aldehydes are contained in an amount of 2000 to 3500 ppm, to provide the amount of oxidization catalyst regulated so as to have no influence on the activity duration of hydrogenation purification catalyst and to provide relevant reaction conditions. In the formation of an aromatic dicarboxylic acid through liquid-phase oxidation of a dialkylated aromatic hydrocarbon with the use of an acetic acid solvent, there have been attained reduction of the amount of acetic acid lost by combustion in oxidation reaction, accordingly suppression of the generation of ash contents in the produced aromatic dicarboxylic acid and regulation of the composition of oxidation catalyst relying on the relationship with reaction temperature. That is, setting the reaction temperature at 185 DEG C. to 197 DEG C., and regarding the values of Co+Mn quantity and Br/Mn ratio calculated from the relational formula correlating them with reaction temperature as regulation levels at least at relevant reaction temperature, catalyst regulation is carried out so that the Co+Mn quantity is 2650 ppm or less with the Br/(Co+Mn) ratio being 1.7 or below.