To provide a manufacturing method which enables the easy manufacture of a high-load transmission belt in which generated centrifugal force is small when running at high speed and its strength is sufficient and a resin material used therein is not melted even in a hot circumstance and its wear-resistance is superior.

In the high-load transmission belt 1 provided with a plurality of blocks 2 arranged in designated pitch intervals along a longitudinal direction of a center belt 3. An insert material 2a is manufactured by stamping a plate material in which a cloth material laminated by a plurality of cloth materials 10 is hardened with a binder 11 made of thermosetting resin, and a covering material 2b made of thermosetting resin is injected and molded on the surface of the insert material 2a as blocks. The blocks are fitted and mounted along the longitudinal direction of the center belt.