Provided is a shelter floating device which enables an amphibious shelter to stably float on a surface of waters. The shelter floating device is provided on a lower surface of the amphibious shelter, and has a protruding floater, a Scott Russell mechanism unit, and a jack (operating means). The protruding floater is connected to the jack through the Scott Russell mechanism unit, while at the same time, being supported by a support device. The jack is fixed to the lower surface of the amphibious shelter. Consequently, by operating the jack, the protruding floater projects itself to an outside of side surfaces of the amphibious shelter along a perpendicular direction.