A magnetic head slider having a plurality of surfaces which are formed sequentially from an adjacent side to a magnetic disk, and a slider rail surface, which is arranged near an air flow-out edge on a nearest surface of the plurality of surfaces including a long sideways rail surface on an air flow-in side and a lengthwise rail surface on an air flow-out side, has a magnetic head. An area of the long sideways rail surface is larger than an area of the lengthwise rail surface.