To provide a power transmission belt and its manufacturing method eliminating the formation of scraps such as chips from cutting, grinding or polishing, preventing a pinhole from being formed near an interface between a cog crest part of a compressed rubber layer and an adhesive rubber layer and preventing early crack initiation during belt traveling.

In the method of manufacturing the power transmission belt, reinforcing cloth 40 and a compressed rubber sheet 55 forming the compressed rubber layer are wound around a molding die 4 alternately provided with projecting parts and groove-like parts, and then pressed under heating by a pressing member 66 alternately provided with tooth parts 64 and groove parts 65, to form an unvulcanized sleeve 60 having an uneven pattern face 68 on a back face 61 together with cog parts. At least a core wire and material forming an extended rubber layer are sequentially wound around the back face 61 of the sleeve having the uneven pattern face 68, to manufacture a belt molding, and then the belt molding is vulcanization-molded by heating and pressing.