To provide a polyester-polycarbodiimide copolymer having both excellent hydrolysis resistance and bending processibility, and to provide the copolymer-containing resin composition useful for an adhesive, coating material or coating.

The polyester-polycarbodiimide copolymer comprises a chemical structure such that a polyester segment (A) having the number-average molecular weight of 5,000-30,000 and a polycarbodiimide segment (B) are interlocked by urethane bonding. The number-average molecular weight of the polyester-polycarbodiimide copolymer is 5,500-50,000. The resin composition containing the copolymer is also provided.