PURPOSE: To easily provide multi-blade fans with various kinds of diameters by constructing a plurality of blade pieces through formation of substantially U-shaped cutting on a bandlike metal flat plate, and cutting and forming them into a cylindrical form.

CONSTITUTION: On a long metal bandlike flat plate wound in a form of roll, cuts 2 are formed to provide a plurality of blade pieces 3. A member 4 comprising the pieces 3 are cut at a required length according to necessities, and the pieces 3 are formed in a required form, then they are formed in a form of cylinder to manufacture a multi-blade fan. It is therefore possible to facilitate the manufacture, execute planned production not depending on orders, produce products with various kind of diameters, and those with the same dia. and different air carrying capacities, which were not produced.