Method for producing fluorinated polyether

Provided is a method for producing, with high yield, a fluorinated polyether having a number-average molecular weight equal to the theoretical value calculated from the number-average molecular weight of a polyether compound of a starting material. A method for producing a fluorinated polyether, which is characterized by comprising a step (1) in which a starting material compound represented by formula (X) and having a molecular weight distribution Mw/Mn of 1.30 or less, an inert gas, a fluorine gas, and a solvent are introduced into a reactor, and the starting material compound is fluorinated. R4-O-(R1-O) x-R5 (X) (R1 represents a divalent hydrocarbon group having 2-5 carbon atoms, R4 and R5 each independently represent a protecting group for a hydroxyl group, and x represents the average degree of polymerization, which is a real number of 2.7-15). 本发明提供以高收率制造根据原料的聚醚化合物的数均分子量计算出的理论值那样的数均分子量的氟化聚醚的制造方法。一种氟化聚醚的制造方法，其特征在于，包含以下的工序(1)：将表示分子量分布的Mw/Mn为1.30以下的由式(X)表示的原料化合物、非活性气体、氟气和溶剂导入反应器中，使所述原料化合物氟化。R4-O-(R1-O)x-R5