To accurately form desired shape with fewer processes using fewer rollers by forming the thickness of an approximately T-shaped portion of the outer diameter side end of a disk-like material to be as thick as possible.

A curved surface roller 3A includes a tip circular arc part 21 with a radius of curvature R satisfying t/2≤R≤10t with respect to the thickness t of the disk-like material, and a plane roller includes a working plane parallel with a roller rotation axis. A control means carries out a first plastic working process for moving the curved surface roller 3A in an inner diameter direction approaching a spindle rotation axis, and allowing the tip circular arc part 21 to abut on the outer diameter surface Wo of the disk-like material W so that a part of the disk-like material W flows sequentially to both end 21a sides along the tip circular arc part 21 to plastically deform the outer diameter side end Wp of the disk-like material W into approximately Y-shape Wy, and a second plastic working process for subsequently pressing the working plane of the plane roller to the inner diameter side from the outer diameter side of the disk-like material W of approximately Y-shape Wy to plastically deform the approximately Y-shape Wy into approximately T-shape.