A flexible printed circuit board of the present invention directly relays connecting portions of a magnetic head placed on a suspension to connecting portions of a base end of a carriage arm in a head suspension assembly of a magnetic disk apparatus. The flexible printed circuit board includes a laminate composed of at least a base layer, a plurality of conductive circuits formed on the base layer, a cover layer covering the conductive circuits, and a conductive polymer layer formed in the insulating material portion in the surface of the laminate. The flexible printed circuit board includes a stainless layer below the base layer or on a lower side of the conductive polymer layer on the base layer side. More preferably, in the magnetic head connecting portion, the cover layer is not formed, and on the base layer in the magnetic head connecting portion, a conductive polymer layer is formed, whereas on the plurality of conductive circuits in the magnetic head connecting portion, the conductive polymer layer is not present or is substantially absent, if any, to such a degree as to allow the magnetic head to be electrically connected to the conductive circuits.