Provided is an effective process for producing a fluorinated polymer excellent in adhesion, by using a polymerization medium having a low ozone layer destruction potential. The process includes polymerizing a monomer mixture comprising a fluorinated monomer and a polar functional group containing monomer (excluding one having a fluorine atom) in a polymerization medium that contains a medium compound represented by CmH2m+1−xFx—O—CnH2n+1−yFy, m is an integer of from 1 to 6, n is an integer of from 1 to 6, x is from 0 to (2m+1), y is from 0 to 2n, and (x+y) is at least 1), and wherein a solution obtained by dissolving the polar functional group-containing monomer in the polymerization medium is continuously or intermittently added to a polymerization reaction system.