A biodegradable polyester is provided. The biodegradable polyester is a transesterification or esterification reaction product of a reactant (a) and a reactant (b). The reactant (a) is a modified linear saccharide oligomer. The reactant (b) is a polyester, or the reactant (b) includes a dicarboxylic acid and a diol. The modified saccharide oligomer is a reaction product of a saccharide oligomer and a modifier.