Abstract: Disclosed is an oxidation reactor for manufacturing terephthalic acid (CTA). In particular, in connection with manufacturing CTA by oxidizing para-xylene in the presence of air containing oxygen and acetic acid solvent, the present invention relates to location relationship among a gas reactant feeding location to feed air containing oxygen, a liquid reactant feeding location to feed para-xylene and a location of an impeller, and also relates to a new oxidation reactor, a structure of which is changed. The oxidation reactor of the present invention controls location relationship among a gas reactant feeding location, a liquid reactant feeding location and a location of an impeller in consideration of a flowing pattern of gas reactant and liquid reactant and a distribution of formed CTA, thereby performing a reaction without a dead zone in the reactor, thus manufacturing CTA in a higher forming rate than before.