To statistically process the surface shape of a magnetic recording medium, and to establish relationship of the floating state of a head slider against the surface shape of a magnetic recording medium.

With a table 11 which moves with a magnetic recording medium 3 being placed on, and a detecting device 12 which detects the surface shape of the magnetic recording medium 3 provided, a control device 13 is provided to control the table 11 and the detecting device 12, and based an the surface shape of the magnetic recording medium 3, the distance between the plane parallel to the surface of the head slider which faces the surface of the magnetic recording medium 3 and the surface of the magnetic recording medium 3 is obtained within the shape dimension of the head slider mounted an a magnetic head.