A polyester resin composition containing 100 parts by mass of a polyester resin and 0.01 to 10 parts by mass of a 2-amino-1,3,5-triazine derivative of Formula [1]: a polyester resin molded body obtained by the composition, and a crystal nucleating agent including the triazine derivative. A polyester resin composition containing a crystal nucleating agent that makes it possible to produce, with high productivity, a polyester resin molded product that promotes polyester resin crystallization and maintains high transparency after crystallization and is applicable for a wide variety of uses can be provided.