To provide a method for producing a fluorinated polymer which enables stable production of a fluorinated polymer having a high molecular weight at a high polymerization rate with good productivity and reduced environmental burdens, a method for producing a fluorinated polymer having functional groups, and a method for producing an electrolyte membrane. A method for producing a fluorinated polymer, which comprises polymerizing a monomer mixture containing tetrafluoroethylene and a fluorinated monomer having a group convertible to a sulfonic acid group or a carboxylic acid group in a polymerization medium, wherein the polymerization medium contains as the main component a C4-10 cyclic hydrofluorocarbon. Further, a method for producing a fluorinated polymer having functional groups and a method for producing an electrolyte membrane, employing the production method.