PURPOSE: To reduce repulsive force in the lapping sections of each layer where both ends of a silicon steel plate are focused, and to close an external wound core easily after mounting winding by mutually displacing the positions of the lapping sections.

CONSTITUTION: The external wound core 5 is constituted by two layers of an outer layer 5a and an inner layer 5b, and the positions of the lapping section D1 of the outer layer 5a and the lapping section D2 of the inner layer 5b are displaced to each other. Accordingly, repulsive force in the lapping section D2 is suppressed by the flat section of the outer layer 5a. Since the positions of both lapping sections are displaced, repulsive force is dispersed, thus weakening repulsive force on the whole.