Thermal conductivity of gaseous refrigerant R 404A was studied by the method of coaxial cylinders within the ranges of thermodynamic parameters 309÷422 K and 0.13÷0.184 MPa. The estimated measurement errors for the temperature, pressure, and thermal conductivity are ± 0.05 K, ± 3.75 kPa, and ± 1.5–2.5%, correspondingly. The approximation dependence for thermal conductivity was obtained for the whole studied range of temperatures and pressures. The results obtained were compared with available published data.