PURPOSE: To magnetize a rotor uniformly by arranging magnetizing heads each prepared by winding a coil around many circumferential magnetic pole teeth on both sides of a rotor and by applying electric current to the coil so that adjacent and opposite pole teeth become heteropolar respectively.

CONSTITUTION: A magnetizing head 1 provided with constant pitch slots 4 is arranged on one side of a rotor 2. Said slots 4 are wound with a coil 5 to form magnetic pole teeth 3. Electric current is applied from a power source 13 so that magnetic pole teeth 3 adjoining each other become heteropolar. Also on the other side of the rotor 2, magnetic pole teeth 1 having just the same structure as that of the former teeth are arranged in the position deviated by one pitch from said former teeth. In this manner, both sides arranged in the perpendicular direction of the rotor can be subjected to heteropolar magnetization and unlike poles arranged in the circumferential direction can be magnetized alternately and uniformly.