Process for producing 1,2,3,4-tetrachlorohexafluorobutane

Disclosed is a process for producing 1,2,3,4-tetrachlorohexafluorobutane safely in a high yield in the industrial viewpoint and at low cost in the economical viewpoint. Specifically disclosed is a process for producing 1,2,3,4-tetrachlorohexafluorobutane which process comprises: (1) a step of chlorinating 1,3-butadiene, thereby preparing a mixture containing 1,2,3,4-tetrachlorobutane, and (2) a step of allowing the 1,2,3,4-tetrachlorobutane prepared in the step (1) to react with a fluorine gas in the presence of a diluting gas in a gas phase, thereby preparing a mixture containing 1,2,3,4-tetrachlorohexafluorobutane.