To solve the problem of conventional system such as that a great deal of work time being required for teeth and slots, since the slots are made between the teeth, along superconducting field winding, by machine processing.

Axial teeth 9 and circumferential teeth 11 are connected to each other by metal spaces 13 being prefabricated connections in the same form as corner parts, whereby the manufacturing time of the winding bobbin 3 can be shortened by the amount of having removed the machine processing for forming the teeth and slots at corner parts.