Holding device and conveying system

A holding device comprising:

• a support member;
• a first holding unit configured to be rotatably supported by the support member and have a first holding portion configured to hold a holding object;
• a second holding unit configured to be rotatably supported by the support member independently of the first holding unit and have 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,
• wherein 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.