Abstract: A laminated retardation plate of the present invention comprises at least two retardation plates made of stretched films of a thermoplastic resin, wherein under the same temperature condition, at least one retardation plate have the relationship of |X1|>|X2|, where X1 represents the dimensional change rate in the direction of slow axis and X2 represents the dimensional change rate in the direction of fast axis; at least one retardation plate have the relationship of |Y1|<|Y2|, where Y1 represents the dimensional change rate in the direction of slow axis and Y2 represents the dimensional change rate in the direction of fast axis; and the each retardation plate are arranged so as to the direction of slow axes thereof are in the same directions. The retardation value variation of the laminated retardation plate is small in the case where the environmental temperature changes.

Abstract: A plurality of test pieces are taken from a long-sized substrate made of stainless steel, where the test pieces are arranged in parallel to the width direction TD of the substrate in a region near the forward end of the substrate. A variation among the curvatures of the test pieces is then measured. A substrate where the variation in the curvature is 0.002 [1/mm] or smaller is selected as a substrate used in manufacture of magnetic head suspensions. While the selected substrate is transported in its length direction, an insulating layer and a conductor layer are stacked on the substrate to form a plurality of magnetic head suspensions.