PURPOSE: To make a correct spiral unit simply preparable, without a necessity of large scale devie, in a manufacturing method of vanes for screw conveyors and guide walls for spiral passages in the generating device of spiral air flow or water flow.

CONSTITUTION: Firstly a metal band-shape plate 1 is provided with cut-in lines in the row arrangement from the both sides toward the inside, with a center portion 2 along the lengthwise direction left for a thin belt, and both side edge parts 3 are constructed into comb-teeth shape respectively with the center portion 2 put between. Subsequently the both side edge parts are folded from the center portion 2 to the inside, simultaneously with a highly strong flocculent material 4, made by intertwining a long fiber like glass fibers, arranged in its interior. Successively with the center portion 2 piled together on a shaft lever 5 and spirally rolled while extending to one side, the both side edge parts 3 of the band-shape plate are radially expanded and opened, followed by a work with the flocculent material 4 also broadly extended. And then with a whole unit of the band-shape plate 1 immersed in a binding material 6, a unified binding material layer is constructed throughout the both side edge parts 3 and the flocculent material 4 to obtain the product.