Abstract: Embodiments of the disclosure relate to a treatment method and a treatment apparatus for a UF6 heel, using a gas phase reaction. A specific treatment method includes (1) vaporizing the UF6 heel, (2) manufacturing solid phase UO2F2 by using UF6 gas vaporized at step (1), (3) separating the solid phase UO2F2 and by-product gas from each other, and (4) separating hydrogen fluoride from the by-product gas. According to the disclosure, stabilization of a reconversion process and the quality of UO2 powder may be improved by manufacturing the solid phase UO2F2, which is an intermediate of the UO2 powder, through the UF6 heel treatment, and the high cost of radioactive waste disposal is reduced by minimizing the UF6 heel to be less than 0.5 kg.