PURPOSE: To prevent defect of projecting parts and improve the yield by integrally molding guards covering the projecting pieces through thin part.

CONSTITUTION: A boss part 2 is formed on a bladed flywheel body 1 and many blades 3 are provided radially as projecting pieces on the outside of the boss part 2. An annular guard 4 covering the blades 3 from the outsides is molded integrally on the outer peripheral part of the bladed body 1. A thin part 5 is provided all over the periphery on the joining part between the guard 4 and the wheel body 1 and the guard 4 is constituted so that is can easily be separated from the wheel body 1 through this thin part 5. Therefore, since the blade 3 is protected by the guard 4 when molding products collide with each other, the blade 3 can be protected from a damage. Further, the guard 4 acts so that it can be separated from the body 1 by the thin part 5.