To provide a transmission belt which will never pollute the environment even though it is burnt and which has excellent heat resistance, oil resistance, abrasion resistance, and flexibility.

A transmission belt has a rubber layer in which core is embedded in adhesion, wherein the rubber layer consists of a crosslinked polymer containing ethylene, ester (metha-)acrylate, and crosslinked component, and the core consists of polyester fiber subjected to a surface treatment with an admixture of resorcinol, formalin, and latex having a carboxyl group.