To provide a device and method for magnetization that can minimize variations in a magnetization pitch, resulting from a speed fluctuation in a driven object.

Along a magnetic layer formed over the circumference of the side edge of a conveying belt, there are arranged in order from an upstream as viewed in the traveling direction of the conveying belt: a first write head 18; a read head 19; and a second write head 20. The first write head 18 and the read head 19 are spaced apart by a half of the belt transport distance for one revolution of a roller which reels the conveying belt (a belt travel distance in a half-period course of the roller). A controller 21 computes, at an operation unit 25, Q3(t) which represents half the sum of a constant pulse interval Q1 of a current during magnetization by the first write head 18 and a pulse interval Q(t) which is read by the read head 19 and detected by a pulse-interval detection unit 24. The magnetic layer is remagnetized by the second write head 20 with a current of the pulse interval Q3(t) which is generated by a pulse-generating circuit 26.