To provide a thermoplastic resin having a narrow molecular weight distribution and suffering reduced discoloration when melt-molded.

The thermoplastic resin is one reduced in thermal discoloration and prepared by radical-polymerizing a raw material containing a vinyl monomer in the presence of an RAFT agent (reversible addition-fragmentation chain transfer agent), optionally decolorizing the obtained polymer by using an oxidizing agent or a nucleophilic reagent, and adding an antioxidant to the polymer. A process for producing the same is also provided.