PURPOSE: To dispense with the rotating work for core assembling at manufacture, easily manufacture an assembly with good working property, and improve the productivity and the degree of freedom in design by mutually combining a plurality of bobbin divided bodies to form a bobbin, and fitting a plurality of cores to the outside of the bobbin.

CONSTITUTION: In a position avoiding a part I to be fitted with a core, assembling parts 16a, 18a such as engaging claw-like protruding parts are formed on one 1a of bobbin divided bodies. Corresponding assembling parts (17a, 19a) such as engaging recessed parts to which the assembling parts 16a, 18a are assembled are formed on the other 1b (which may be the same form as the bobbin divided body 1a) of the bobbin divided bodies, and the bobbin divided bodies are combined together by the assembling of both the assembling parts to form a bobbin.