The method of solidifying residue containing rare

PROBLEM TO BE SOLVED : To provide a method for solidifying a rare earth-containing residue, in which a large amount of the acidic residue, that is generated when rare earths are extracted from rare earth-containing mud by using an acid, can be treated easily and the treated residue can be utilized as a buried material or the like.SOLUTION : The method for solidifying the rare earth-containing residue comprises a step of mixing the acidic residue, which is generated when the rare earth-containing mud (for example, the mud that exists in the sea bottom ground and has 1, 000 ppm or higher rare earth content) is treated with the acid, with an alkaline solidifying material to obtain a solidified body. The alkaline solidifying material contains, for example, cement, lime or magnesium oxide.