Abstract: An unmanned conveying device for a clean room is capable of restraining a spontaneous oxide film from growing in case that an unmanned carriage is obliged to stop for a long time due to its own cause of a cause at a destination spot while it conveys a semiconductor wafer from one spot to the destination spot. It is a first aspect of the invention to provide the unmanned conveying device which is self-propelled for conveying an object from a ground facility to a destination spot while loading an object to be conveyed thereon, characterized in that the object is accommodated in a container and the container is connected to an inert gas reservoir through a gas supply passage so that the atmosphere in the container can be replaced by a nitrogen gas.