A disk device rotates a disk-like storage medium, and accesses the storage medium, and a slider floats over a storage medium by the action of an airflow caused by rotation of the storage medium and can float stably despite of an environmental change. An inner rail formed on a floating surface of the slider has a first step part located on an air inlet side and a second step part located adjacent to the first step part on the air outlet side and having a height greater than that of the first step part, and the first step part and the second step part are separated by a wall along a first segment extending from an inner side toward an outer side and a second segment extending from the outer-side end of the first segment toward the outer side with being slanted toward the air inlet side.