PURPOSE: To improve the yield of a product and electric current efficiency by making a specific aliphat. nitrile present in a process which executes the electrolytic decarboxylation of a perfluoropolyether expressed by a specific general formula.

CONSTITUTION: The perfluoropolyether expressed by formula II is produced by the electrolytic decarboxylation of the perfluoropolyether expressed by the general formula I. In the formula I, (x) denotes an integer from 1 to 4. In the formula II, (x), (y) denote an integer from 1 to 4. At this time, the electrolytic decarboxylation is executed in an aq. electrolyte in the presence of an aliphat. nitrile having 1-6C alkyl group. More preferably the electrolytic decarboxylation is preferably executed at -10 to 90°C and a current density of 20 to 500 mA by using acetonitrile, propionitrile or isobutyronitrile as the aliphat. nitrile and using the electrolyte contg. 1 to 50 wt.% aliphat. nitrile.