PURPOSE: To eliminate a process for impregnating or coating a synthetic resin and a process for eliminating burr of a cured resin for improving productivity by storing a magnetic core where a magnetic material is laminated and by performing injection and filling of a molten synthetic resin for impregnating or coating the synthetic resin.

CONSTITUTION: A toroidal core-shaped magnetic core 2 is constituted by winding a thin amorphous metal film 1. After performing annealing, the magnetic core 2 is stored inside a first mold, molten resin is injected and filled, a synthetic resin is impregnated or coated between the thin amorphous metal films 1 and fixed, and at the same time the surrounding of the magnetic core 2 is covered. A resin to be used should be selected according to the performance required to a core and especially nylon, polyethylene, polyacetal, and a mixture of a reinforced material such as fiber glass to them are suitable.