To provide a method of isomerizing 3H-heptafluorocyclopentene and 4H-heptafluorocyclopentene.

The 3H-heptafluorocyclopentene and/or the 4H-heptafluorocyclopentene can be isomerized into 1H-heptafluorocyclopentene by causing the same to contact a metal fluoride. By using the process, 1H-heptafluorocyclopentene of higher purity can be obtained. Specifically, the method of producing 1H-heptafluorocyclopentene includes: dehydrofluorinating 1H, 2H-octafluorocyclopentane to produce 1H-heptafluorocyclopentene comprising 3H-heptafluorocyclopentene and/or 4H-heptafluorocyclopentene; isomerizing the resulting 3H-heptafluorocyclopentene and/or 4H-heptafluorocyclopentene present in the 1H-heptafluorocyclopentene; and subsequently distilling the reaction product to obtain highly pure 1H-heptafluorocyclopentene.