To provide a wheel disk comprising an annular base bolt-fastened to a wheel hub, a first rim radially expanded while extending in one direction along the axis from the outer edge of the base, a second rim radially expanded while extending in the opposite direction along the axis from the outer edge of the first rim, and a tire-fitting rim formed along the outer edge of the second rim, and capable of enhancing its rigidity to cope with easy inclining deformation caused by the fluctuation of a load applied to a wheel since an annular part of a ridge-shaped section composed of the first rim and the second rim is relatively flexible.

A disk-shaped or star-shaped rib member for firmly connecting at least two parts separated from each other along a ring of a first rim is provided on the wheel disk.