The invention discloses a mold for sewing a belt buckle and a belt and a sewing device. The mold comprises a mold soleplate, wherein a belt buckle grooved plate is arranged on the mold soleplate, and the upper surface of the belt buckle grooved plate extends inwards from the edge end to be provided with a belt buckle groove; a sewing hole is formed on the mold soleplate, and the sewing hole is arranged on the side edge of a notch of the belt buckle groove. The mold soleplate is also provided with a belt track, the belt track faces the notch of the belt buckle groove, and the belt track, the sewing hole and the belt buckle groove stay on the same central axis. The belt track consists of two parallel stop bars which are spaced apart. The belt buckle and the belt, which are to be sewed and well fastened, are fixed on the mold, a sewing position is arranged in the sewing hole, and the sewing area is sewed in the sewing hole through a sewing needle, so that safety in operation is realized, and the working efficiency is improved.