To provide a method for improving the strength of crosspieces and a V-belt and for producing a product of stable quality efficiently in the V-belt with crosspieces having functions of scooping up a crop such as rice and wheat and conveying it.

A liquid polyurethane is injected in the clearance between an inner mold 20 having a crosspiece cavity 21 with the shape of the crosspiece carved in the inside and an outer mold 10 having a main body cavity 11 with the shape of the V-belt carved in the inside and solidified to make a belt sleeve with crosspieces. The V-belt with the crosspieces is produced efficiently by cutting the belt sleeve in a prescribed width.