To provide an automatic air-feeding mechanisms which can produce a large amount of compressed air with a small number of rotations of a wheel body and with a small force. The automatic air-feeding mechanisms has first and second compressed air producing sections 1a and 1b, and pneumatic tire compressed air supply passages 2a and 2b for introducing the compressed air produced in the compression air producing sections to a pneumatic tire. The first and second compressed air producing sections 1a and 1b are attached to a hub drum 102a of the hub 102 at positions 180.degree. apart from each other. When the wheel body is rotated, the first and second compressed air producing sections 1a and 1b alternately produce compressed air.