PURPOSE: To improve strength characteristics in the temperature range of 100 to 200°C without impairing conductivity and flexibility by a method wherein a copper wire, having a fiber-like structure on which crystal is extended in longitudinal direction and also having specific purity adjusted to the specific yield strength, is used.

CONSTITUTION: As the abundance rate of a grain boundary can be reduced and also as the stable spreading of cracks in right-angled direction can be blocked by obtaining a fiber-like structure on which crystal is extended in longitudinal direction, the thermal fatigue cracks and their spreading generated in response to a heat cycle can be prevented effectively. Also, the dislocation in a matrix can be reduced by adjusting the 0.2% yield strength to 15 to 35kgf/ mm2, and an excellent coil-winding property can be maintained by giving sufficient flexibility. Moreover, electric resistance can be made small by using a copper wire having the purity of 99.99% or higher. Accordingly, a highly strong winding, on which thermal fatigue due to the difference in linear expansion coefficient of the epoxy resin covering the whole body is controlled in the temperature region of 100 to 200°C, can be obtained.