PURPOSE: To make is possible to facilitate the handling and manufacture of a spin weld bobbin and to have a sufficient strength even though it has a large size, by disposing a partition member spanning between end faces of each adjacent sections, and by welding between the partition member and the contact surfaces and end faces of each adjacent sections with the use of a spin weld process.

CONSTITUTION: In the case of forming a bobbin integrally from resin molded sections, a partition member 20 is welded and fixed to a half 10 of the bobbin by use of a spin weld process. In this phase, when the partition member 20 has entered into the half 20 by one-half of the axial length of the member 20, it is stopped and welded. By integrally joining both halves 20, 12 of the bobbin with the use of the spin weld process, it is possible to obtain a bobbin having a barrel 14 and a shaft 18 which are coupled together. With this arrangement, it is possible to obtain a spin weld bobbin which is lightweight so as to be easily handled even though it has a large size, and has a sufficient strength while it may be easily manufactured.