Abstract: A cushion includes a three-dimensional net, a plurality of metallic fastening members attached to the three-dimensional net on opposite sides thereof, and two resinous frames attached to the opposite sides of the three-dimensional net, respectively. The metallic fastening members are sandwiched between the resinous frames and the opposite sides of the three-dimensional net, and the resinous frames together with the metallic fastening members are joined to the three-dimensional net by vibration welding.