In a method for manufacturing a shaft, and surfaces of a pair of metal sheets are polished, and the metal sheets are each bent into a cylindrical or arcuate shape. The polished end surfaces of the metal sheets are butted together with the end surfaces facing each other. The butted end portions are diffusion-joined, thereby forming a cylindrical member. The cylindrical member is cooled, and ends of the cylindrical member are joined to linking members to form the shaft.