PURPOSE: To obtain a core having low iron loss by forming an amorphous alloy thin strip in a specific backing factor, then heat treating it, curing it, then impregnating it with resin in specific Shore hardness, and cutting it.

CONSTITUTION: When winding a core, backing factor is set to 75W85%. The backing factor is the ratio of the weight of the core after molding to a theoretical weight, and the theoretical weight is obtained by attaining the volume of the core with the outer, inner diameters and the height of the core after molding and multiplying the volume by the specific weight of an amorphous alloy. When the heat treating temperature T at heat treating time is preferably in a range of the temperature range of TX-100°C<T<TX, where the heat treating temperature (°C) is T and crystallizing temperature (°C) is TX. The hardness after curing in case of impregnating it with resin is 50W70 of Shore hardness. The impregnating and hardening of the resin prevent the core from deforming due to cutting grindstone when cutting it and cutting resistance with high hardness amorphous alloy, such as the opening between the layers of the cutting surfaces by the fixture of the core.