The present invention relates to a method for preparing N-(4-acetyl-2,6-difluorophenyl)methanesulfonamide, the method comprising a step of reacting 3,4,5-trifluoroacetophenone and methanesulfonamide in the presence of a nitrile solvent. The preparation method of the present invention enables a high yield of INT-1 to be prepared easily, particularly without involving a metal catalyst and without producing impurities. Therefore, by being more economical than other methods in that a metal catalyst is not involved and enabling INT-1 to be obtained with high yield, the method can be useful in the field of INT-1 preparation.