PURPOSE: To produce a precise and high-reliability main magnetic pole disc inexpensively, by forming a thin film patter, which has a required shape and consists of a soft magnetic metal, on a magnetic tape by adhesion and forming a recessed part, where each thin film pattern exists, on a disc by coining.

CONSTITUTION: Plural main magnetic poles 11a, 11b, 12a, and 12b arranged on a disc 4 are formed with thin films 21a, 21b, 22a, and 22b provided simultaneously on a disc 20, and respective thin films are formed by simultaneous patterning. The patterning is performed on the basis of a center hole 30 of the disc 20. A coining mold 34 is worked by the precise working technique such as an ion beam work, and the coining work is performed on the basis of the center hole 30 of the disc 20 also. Thus, plural main magnetic poles are worked and formed simultaneously without manual operations, and the disc where the out of roundness of the circle of main magnetic poles is very precise and high-reliability is produced inexpensively.