To provide a transmission belt and a manufacturing method thereof, favorably maintaining the arrangement of core wires to prevent the generation of a void between the core wires and inhibit dynamic separation of core wires, having durability, and lowering the cost.

In this transmission belt 1, an adhesive rubber layer 3 is disposed to enclose the core wire 2 formed of cords along the longitudinal direction of the belt, a rib rubber layer 4 is provided to closely adhere to the adhesive rubber layer 3, and canvas is not stacked on the back 5 and the inside part to expose the respective rubber layers 3, 4. Since the adhesive rubber layer 3 is provided to completely enclose the periphery of the core wires 2, turbulence of the core wires 2 is not caused in pressing in a rubber composition, and also compressive deformation of the core wires 3 is avoided to prevent the generation of a void, so that stable running of the belt is secured, and separation in the interface between the core wires and the adhesive rube is not caused. The component members are decreased in number to provide the transmission belt at a low cost.