According to a production method of a power transmission belt, a shaped structure having a cylindrical shape is placed radially inward of belt mold having a cylindrical shape. The shaped structure is provided on a mandrel and has a plurality of ridges arranged adjacent to one another in an axial direction of the shaped structure. The belt mold has a plurality of compression layer-shape grooves arranged adjacent to one another in an axial direction of the belt mold. The shaped structure is crosslinked by heating and pressing the shaped structure toward the mandrel while each of compression layer-forming portions, which are comprised of the plurality of ridges of the shaped structure, is fitted in an associated one of the compression layer-shape grooves of the belt mold, thereby molding a cylindrical belt slab.