PURPOSE: To obtain a compound useful as a trifluoromethylating agent in a short time safely and in high yield, by reacting trifluoroacetic anhydride with hydrogen peroxide in the presence of sodium carbonate and/or potassium carbonate.

CONSTITUTION: Trifluoroacetic anhydride is reacted with hydrogen peroxide in the presence of sodium carbonate and/or potassium carbonate in the molar ratio of 1:0.05W2.0:0.05W3.0 at -20-0°C for 20-60minutes to give the aimed substance. This compound is useful as a trifluoromethylating agent of trifluoromethylating compounds suitable as synthetic intermediates for polymerization initiator, drug, agricultural chemical, etc. Since a specific production device is not required in production, this method is also industrially effective.