To easily process even a cylindrical component having a disproportionate shape in a plate thickness or a volume.

This spinning method processing a rotor shaft includes a material junction process, a material separation/deformation process, and a cylinder formation process. In the material junction process, the plate surfaces of two or more metal plates 40a, 40b, 40c are overlapped and joined. In the material separation/deformation process, the metal plates 40a, 40b, 40c are rotated by a rotary shaft CL perpendicular to the plate surfaces, and the metal plates 40a, 40b are separated and deformed by applying force to junction positions of a peripheral part of the two or more joined metal plates 40a, 40b, 40c. In the cylinder formation process, force is applied to one or more metal plates 40a, 40b, and a cylinder along the rotary shaft CL is formed.