According to one embodiment, a disk device comprises a plurality of rotatable magnetic disks, a first actuator assembly, and a second actuator assembly. A slit provided in each of arms of the first actuator assembly is provided to be offset in a direction spaced away from a border plane between actuator assemblies with respect to a center of the arm in its thickness direction. A connection end portion of a wiring member is partially located in the slit, such as to be offset in a direction spaced away from the border plane, and disposed on a wiring board, and joined to the wiring board.