PURPOSE: To manufacture a hollow spherical body simply, by forming the body of a sphere by plastic working a tube or a steel plate, providing screw caps of arcuate face having the same thickness, forming thread on inner peripheral face of the opening of the sphere body and outer peripheral face of the screw caps and threadedly engaging them.

CONSTITUTION: A straight cylindrical tube material 4 is cut to a prescribed length and the body of a sphere 7 is formed by upper and lower bowl-shaped dies 5, 6. Then, internal threads are cut on inner peripheral faces of openings 8, 9 of the sphere body 7. Further, caps 10, 11 having arcuate faces of the same curvature with the body of the sphere 7. External threads that engage with internal threads cut on inner peripheral faces of openings 8, 9 of the body of the sphere 7 are cut on outer peripheral faces. After screwing the caps 10, 11 in the openings 8, 9 of the body of the sphere 7, outer face of the screwed part is welded. After welding, the surface of the sphere is polished, and a hollow spherical body is obtained.