The present disclosure relates to a method of removing a radioactive structure from a nuclear power plant. The method includes flattening at least a portion of an outer surface of a drilling portion of a wall of a nuclear reactor vessel when the portion of the outer surface is uneven, wherein the radioactive structure is buried in the wall and the drilling portion is adjacent to the radioactive structure, installing a drilling device in the flattened drilling portion and performing a drilling operation, extracting the radioactive structure from the wall, and cutting the extracted radioactive structure and storing pieces of the cut radioactive structure in a shielding container.