Embodiments of the invention provide a disk device capable of diminishing oscillation of a disk caused by an air flow which is created with rotation of the disk. In one embodiment, a magnetic disk device comprises a rotatable magnetic disk, a base and a top cover for housing the magnetic disk inside, a flow uniforming wall disposed along an outer periphery of the magnetic disk, and a circulation filter for collecting dust present within the device. The flow uniforming wall is positioned in opposition to the outer periphery of the magnetic disk and has a step height at a position other than the position opposed to the disk outer periphery, with an opening being formed by a gap between the step height and the top cover. This opening serves as an inlet port to admit an air flow created with rotation of the magnetic disk, and the circulation filter collects dust contained in the admitted air flow.