To efficiently obtain a rotary symmetry shaped steplike body from a single tube part by fixing a single tube end part of a tube part as a start forming product of the steplike body to be produced with a spinning jig, holding the tube end part to form an outside cylinderlike part in non-rotating with the spinning jig and supporting the tube part to be formed with end support onto the free tube end.

A central bore 33 of a supporting jig 6 is formed for receiving a centering mandrel 43 of a spinning jig 4 and a forming mandrel 40. A tube part 8 as a start forming product of a steplike body to be produced is only one tube end part 13 and it is fixed with the spinning jig 4, and it is clamped by one side with this. The tube end part 13 to be fixed is tightened with a tightening ring 41, the tightening ring 41 is slid or bent on the tube part and reached to the edge of forming product to be formed. The tube end part of opposing in the projected part 18 to be formed of the tube part 8 is named as a free tube end 23 and it is supported to a flat part 26 of the supporting jig 6 only with the end face.