NOVELTY - Tetrachloroethylene and hydrogen fluoride are reacted, and rough pentafluoroethane (I) is produced. Pressure of rough pentafluoroethane is increased to 0.1 MPa or more. The resulting product is distilled into high-boiling point component (II) and low-boiling point component (III). Component (III) is contacted with specific gas permeation membrane, and permeation gas (IV) and impervious gas (V) having pentafluoroethane are separated. Gas (V) and reaction gas are mixed to produce rough pentafluoroethane, which is recycled. Thus, pentafluoroethane is manufactured.    USE - For manufacturing pentafluoroethane used as coolant, foaming agent, propellant, etching gas and cleaning gas.    ADVANTAGE - Pentafluoroethane having high purity is efficiently and continuously manufactured.    DETAILED DESCRIPTION - Tetrachloroethylene or its fluorinated material and hydrogen fluoride are reacted in the presence of a fluorinated catalyst, and a reaction gas containing at least pentafluoroethane, non-condensable gas and other fluorocarbon is produced. The pressure of obtained rough pentafluoroethane (I) containing reaction gas is increased to 0.1 MPa or more by compression. The resulting product is distilled and separated into high-boiling point component (II) containing pentafluoroethane as main component, and low-boiling point component (III) containing at least pentafluoroethane, noncondensable gas and fluorocarbon. The component (III) is contacted with a gas permeation membrane consisting of a polymer having poly (4-methyl pentene-1) as main component, and a permeation gas (IV) and impervious gas (V) are separated. The gas (V) contains pentafluoroethane as main component. The gas (IV) contains pentafluoroethane, non-condensable gas and fluorocarbon. The gas (V) and reaction gas are mixed to produce rough pentafluoroethane, which is recycled. Thus, pentafluoroethane is manufactured.    DESCRIPTION OF DRAWING(S) - The figure shows process flowchart illustrating the manufacture of pentafluoroethane.    Rough pentafluoroethane (I)    High-boiling point component (II)    Low-boiling point component (III)    Permeation gas (IV)    Impervious gas (V)