PURPOSE: To reduce an eddy current loss, by composing an armature yoke wound up with a magnetic substance band in an eddy shape, in the state of placing an insulating layer between wound-up layers.

CONSTITUTION: The one side surface of a wide, long, and thin magnetic substance sheet 10 is coated with an insulating film having adhesive property. The magnetic substance sheet 10 is wound up in the eddy shape of much frequency so that the dimension may be almost equal to the diameter dimension of an armature yoke 1. After that, this wound-up unit 11 is cut off with a specified thickness dimension along a surface orthogonal to the axial direction, and the armature yoke 1 in an eddy shape is formed. Then, on the surface of the armature yoke 1, armature coils 2 are arranged and fixed, and a stator 3 is formed. As a result, without increment on an industrial cost and difficulty on manufacture, the loss of eddy current can be reduced.