According to one embodiment, a holding device includes: a support member; a first holding unit having a first holding portion configured to hold a holding object; a second holding unit having a second holding portion configured to hold the holding object; and a controller configured to control an operation of the first holding unit and the second holding unit. The controller is configured to switch which of the first holding unit and the second holding unit is used for holding the holding object, by rotating the first holding unit and the second holding unit in a state where the first holding unit and the second holding unit face different directions, and control to change an orientation with respect to the support member, by rotating at least one of the first holding unit and the second holding unit with respect to the support member.