To prolong a lifetime by maintaining the position of a core in a center belt constant, improving the accuracy of a PLD, thereby stabilizing feeding of the belt, and reducing a problem of oblique feeding of a block and a noise.

The method for manufacturing the center belt for a high load transmission belt fixing the block to the center belt comprises the steps of winding a core 5 on an inner mold 40 having a protruding strip 41 for forming a recess strip 19 of the center belt and a protrusion 41 for positioning the core, further winding an unvulcanized rubber sheet G, pressurizing and heating the sheet to cast rubber through the core between the protruding strips of the inner mold, forming the recess strips 19 on the inner peripheral surface of the center belt and vulcanizing the strips.