To provide a transmission belt wherein adhesive force between each core wire and an adhesive rubber layer is improved.

The transmission belt 1 comprises the adhesive rubber layer 3 in which the core wires 2 are embedded along a belt longitudinal direction, and an elastic material layer including a compressed rubber layer 4. The core wires as cords each having a coat formed with adhesion processing agent incorporating 5-25 pts.mass fatty acid or/and fatty acid derivative, as processing material, and a 10-20 pts.mass isocyanate compound in 100 pts.mass ethylene--olefin-diene copolymer having a diene content of 8-20% is embedded in the adhesive rubber layer formed of an ethylene--olefin rubber composition.