To reduce weight and cost while preventing a rubber part from being peeled off.

A rubber mounting part 24, which is bent to have a substantially L-shaped cross section at a front edge side over an entire circumference of a rim 12 in a drum surface state, is provided to a portion near to the outer peripheral side of the disk-like rim 12. The rubber part 28 is integrally vulcanized and adhered on the circumference of the rubber mounting part 24, and the rubber part 28 is formed in a shape to be slanted and widened in width from its inner peripheral edge toward the outer peripheral side. The rubber mounting part 24 is provided with a plurality of through-holes 26 interconnecting the rubber parts 28 on the front and rear surfaces of the rubber mounting part 24 circularly disposed at prescribed intervals. An outer peripheral side bent part 22 formed by bending the face of the rim 12 is provided on the rim 12 at the inner peripheral side of the rubber part 28 adjacent to the rubber part 28.