To prevent a felt or a canvas from separating from the back surface of a belt by infiltrating a thermoplstic resin under a molten state in the felt or the canvas, and integrally bonding the back surface of the belt and the felt or the canvas when the belt comprising a thermoplastic resin, wherein a core wire is embedded.

When a toothed belt is manufactured, first, a back surface canvas and a felt are fed out from a canvas feeding machine 33 or a felt feeding machine, and fed to a steel band 13 from a canvas inserting machine 33 or a felt inserting machine, and fed to a die roll 17 together with the steel band 13. Also, a tooth surface canvas is fed out from a canvas feeding machine 37, and is fed to the die roll 17 from a canvas inserting device 26. Then, a molten resin is extruded from an extruder 15, is laminated on a core wire 4, and is made to flow into a cavity between the back surface canvas or the felt and the core wire 4. Then, on the die roll 17, the tooth surface canvas, the core wire 4, and back surface canvas or the felt, and the steel band 13 are laminated in this order, and at the same time, the core wire 4 is embedded in the molten resin, and the resin is molded into the shape of the toothed belt.