A polyester elastomer is provided, which includes a product of reacting (a) amide oligomer, (b) polyalkylene glycol, and (c) poly(alkylene arylate). (a) Amide oligomer has a chemical structure of or a combination thereof, wherein R1 is C4-8 alkylene group, R2 is C4-8 alkylene group, and each of x is independently an integer of 10 to 20. (b) Polyalkylene glycol has a chemical structure of wherein R3 is C2-10 alkylene group, and y is an integer of 20 to 30. (c) Poly(alkylene arylate) has a chemical structure of or a combination thereof, wherein Ar is R4 is C2-6 alkylene group, and z is an integer of 1 to 10.