Method for producing fluoropolymer

A method for producing a fluoropolymer, the method comprising:

• polymerizing a monomer (I) represented by the general formula (I) below in an aqueous medium substantially in the absence of a fluorine-containing surfactant (except for the monomer (I) represented by the general formula (I)) to obtain a crude composition containing a polymer of the monomer (I);
• removing a dimer and a trimer of the monomer (I) contained in the crude composition from the crude composition to obtain a polymer (I) in which the content of the dimer and trimer of the monomer (I) is 1.0% by mass or less based on the polymer (I);
• and
• polymerizing a fluoromonomer in an aqueous medium in the presence of the polymer (I) to obtain a fluoropolymer:
• CX1X3═CX2R(—CZ1Z2-A0)m (I)
• wherein X1 and X3 are each independently F, Cl, H, or CF3;
• X2 is H, F, an alkyl group, or a fluorine-containing alkyl group;
• A0 is an anionic group;
• R is a linking group;
• Z1 and Z2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group;
• and m is an integer of 1 or more.