PURPOSE: To form a magnetic layer having coercive force at a high speed by forming the magnetic layer consisting of a Co alloy on the surface of a base by an ion plating method by making the kinetic energy of the ion of the element to be added to Co larger than that of the Co ion.

CONSTITUTION: Co 6 and an element M7 to be added are put into respectively separate tanks of, for example, a vapor source 5 in the stage of forming a magnetic layer 4 consisting of a two-element alloy such as C-Cr, Co-Mo or a three- element alloy such as Co-Cr-Mo by an ion plating method on a base consisting of polyethylene terephthalate, etc. Said elements are polarized respectively as Co vapor flow 8 and M vapor flow 9 by deflecting magnetic fields 12, 15 and are stuck thereto. The kinetic energy of the element M ion is made larger than the kinetic energy of the Co ion in this stage. Co+ is made to 600eV and Mo+ to 1,000eV in order to obtain, for example, an Mo 20.5wt% film of Co-Mo at a rate of about 4,000/sec, by which the vertical magnetized film 4 having high coercive force of about ≥1,000Oe is formed.