Polymer composition, molded body, optical member and method for producing polymer composition

A polymer composition comprising a polymer comprising a monomer unit having a ring structure,

• wherein the polymer composition is a polymer composition A comprising a polymer of a monomer having a ring structure, or a polymer composition as a cyclized product of a polymer composition B containing a precursor polymer, namely a polymer of two or more different monomers that are capable of together forming a ring, and
• when a flat plate of 120 mm×100 mm×3.0 mm in thickness is molded from the polymer composition under the following injection molding conditions of:
• (1) using a non-vent-type injection molding machine;
• (2) using a cold runner mold;
• (3) having a cylinder temperature of 260° C.;
• and
• (4) having a ratio of an injection volume of the injection molding machine to a molded product volume of 4.5, and wherein
• a difference between a monomer content in the flat plate obtained at a cooling time of 5 min and a monomer content in the flat plate obtained at a cooling time of 1 min is 1000 ppm by mass or more and 12000 ppm by mass or less.