It is an object of the present invention to provide a power transmission belt which is superior in dynamic adhesion and heat-resistant adhesion against repeated flexing of a power transmission belt or running under heating conditions around an engine, and is also superior in heat resistance, abrasion resistance and an abnormal noise-preventing property.The present invention pertains to a power transmission belt in which an adhesive rubber layer in which core wires are embedded along the longitudinal direction of the belt is bonded by vulcanization to a compressed rubber layer laminated on the inner surface of the above-mentioned adhesive rubber layer, wherein the above-mentioned adhesive rubber layer and the above-mentioned compressed rubber layer are formed by using ethylene-α-olefin-diene rubber compound, and the diene content in ethylene-α-olefin-diene rubber of the above-mentioned adhesive rubber layer is equal to or larger than the diene content in ethylene-α-olefin-diene rubber of the above-mentioned compressed rubber layer, and the diene content in ethylene-α-olefin-diene rubber of the above-mentioned adhesive rubber layer is 3.5 to 10% by mass and the diene content in ethylene-α-olefin-diene rubber of the above-mentioned compressed rubber layer is 0 to 6% by mass.