To provide an expansion device and a movable body including a mechanism for quick deformation. An expansion device includes a main body and a limb portion attached to the main body, in which the limb portion includes a main link connected to the main body via a joint, an end link provided at a front end of the limb portion, at least one or more limb joints that are interposed between the main link and the end link and connect the main link and the end link, and a linear member of which both ends couple an end at the front end side of the limb portion of the end link and the main body and are retractable to one or both of the end link and the main body.