PURPOSE: To prevent the breakage of a winding conductor by a construction wherein an annular core is provided with a slotted spacer on at least one peripheral surface and the winding conductor is wound through slots of the slotted spacer.

CONSTITUTION: A slotted spacer 3 is provided on at least one peripheral surface of an annular core 1, and a winding conductor 2 is wound through slots 4 of the slotted spacer 3. By so doing, there can be obtained a current transformer in which the winding conductor 2 will not undergo the load and will be prevented from breakage. Since the winding conductor for secondary winding thus arranged will not be directly subjected to the load, it becomes possible to eliminate the load applied and to prevent breakage of the winding conductor, thereby preventing the winding conductor from breaking.