According to one embodiment, a disk device includes a disk, a drive section which is configured to support and rotate the disk, a head, and a head actuator assembly. The head actuator assembly includes a board unit including a base portion on which an electronic component is mounted, a main flexible printed circuit board which is configured to extend from the base portion and have a connecting end portion attached to the carriage, and a reinforcing plate including a bent portion fixed to the main flexible printed circuit board, and a vibration damper which is configured to include a sheet-shaped viscoelastic material stuck on the bent portion and a sheet-shaped reinforcing material, more rigid than the viscoelastic material and stuck on the viscoelastic material in superposed relation, and suppress vibration of the reinforcing plate.