According to one embodiment, a disk device includes rotatable magnetic disks, a first actuator assembly rotatably supported on a pivot through a first bearing unit, a second actuator assembly rotatably supported on the pivot through a second bearing unit and provided side by side with the first actuator assembly in an axial direction of the pivot, and a filter unit provided between the magnetic disks and the first and second actuator assemblies. The filter unit includes a holder including a shielding portion facing a boundary portion between the first actuator assembly and the second actuator assembly and a ventilation opening provided at a position spaced apart from the boundary portion in the axial direction, and a filter held by the holder and facing the ventilation opening.