PURPOSE: To reduce noise generated by magnetic strain vibration by laminating directional silicon steel having scratches provided parallel in a rolling direction on the surface and directional silicon steel having a negative magnetic strain against a magnetic flux.

CONSTITUTION: Directional silicon steel 2 having scratches 1 provided parallel in a rolling direction on the surface shows a positive magnetic strain against a magnetic flux. This directional silicon steel 2 and directional silicon steel 3 having a negative magnetic strain against a magnetic flux are alternately laminated to form a magnetic iron core. The scratches 1 should be deep to such an extent that a film provided on the surface of the directional silicon steel may not be broken. They also may be provided at a slight angle with a rolling direction. The directional silicon steels having a positive and a negative magnetic strain react against each other, thus reducing noise generated by magnetic strain vibration.