PURPOSE: To improve the output on the short wavelength side by setting A/B (A is the product between the coercive force and the residual magnetization measured at 60° from the lengthwise direction to the perpendicular direction and B is that measured in the lengthwise direction) to ≥0.75 and setting A to ≥4MGOe.

CONSTITUTION: A magnetic paint including magnetic powder, a binder, etc., is applied on a nonmagnetic supporting body 2 to form a magnetic coating film 3, and the magnetic field inclined at an angle θ from the lengthwise direction to the perpendicular direction is applied to a film 3 to orientate the film 3. The angle θ is set to 10 to 60°, and it is difficult that A/B is ≥0.75 if the angle θ is not within this range, and it is preferable that the intensity of the magnetic field is about 2000 to 7000G. The film 3 is dried in the magnetic field while the magnetic field is applied, and the film is subjected to smoothing treatment and is hardened. The output on the short wavelength side is not sufficient if A/B is <0.75, and its upper limit is set to about 0.95. The output on the short wavelength side is not sufficient if A is <4MGOe, and it is difficult to considerably increase it; and therefore, A is set to about 4 to 5MGOe normally.