PURPOSE: To enable elimination of transmission noise as usual and facilitate operation in production of cables by providing a ferrite core with which the whole outside of an insulator is covered, and providing on the outside an outer covering layer protecting the ferrite core.

CONSTITUTION: A conductor 1 is arranged innermostly, an insulator 2 for insulating the conductor 1 is provided thereon, then a ferrite core 3 thereon and an outer covering layer 4 outermostly. The ferrite core 3 serves to cover the insulator 2 for eliminating noise flowing in the conductor 1, and the outermost layer serves to protect them. In this core-incorporated cable, transmission line has an extremely high impedance against high frequency noise with higher frequency component than signals, and action to block the current therein occurs to attenuate noise current to thereby prevent the effect of noise.