According to one embodiment, a disk device includes a first actuator assembly and a second actuator assembly which are respectively supported by a first bearing unit and a second bearing unit to be rotatable about a support shaft. The first bearing unit includes a first sleeve and a ball bearing. The second bearing unit includes a second sleeve and a ball bearing. The first sleeve includes a first end surface opposed to the second sleeve and an annular first step projecting from the first end surface, and the second sleeve includes a second end surface opposed to the first step with a gap and an annular second step projecting from the second end surface. The second step is opposed to the first step and the first end surface with a gap.