PURPOSE: To efficiently remove impurities such as bromotrifluoromethane contained in trifluoromethane by allowing gaseous trifluoromethane to pass through an adsorbent layer containing activated carbon.

CONSTITUTION: This method for purification of trifluoromethane is carried out by taking out the raw material trifluoromethane 1 in a gas state through a reducing valve 2 from a gas cylinder accommodating it in a liquid state, cooling the discharged gas through a coiled tube 4 in a cooling tank 3, then allowing it to pass through an activated carbon-containing absorbent layer 5 cooled also in the cooling tank 3 while keeping it in gas state and collecting the gas as the objective high-purity trifluoromethane having passed through the adsorbent layer 5 and discharged through a pressure control valve 7. The gas layer passing through the adsorbent layer 5 is controlled to -32±3°C and atmospheric pressure to 10-kgf/cm2. The adsorbent layer 5 contains preferably one or more kinds of substances selected from a group of activated carbon, molecular sieving carbon, activated carbon fiber and activated carbon-coated silica alumina. The adsorbent layer can be activated and regenerated by calcination or steam treatment. The adsorptivity is not deteriorated even after adsorption and regeneration are repeated.