A method of preparing an intermediate useful for the synthesis of a diphenylmethane derivative that can be used as an SGLT inhibitor is described. A method of synthesizing a compound of Formula 7 can address problems of existing synthesis processes requiring the synthesis of the Grignard reagent and management of related substances. In addition, the method can minimize the generation of related substances, and thus does not require reprocessing of reaction products, thereby simplifying the process. Accordingly, the production yield of a diphenylmethane derivative can be maximized.