To provide a simple-structured low-temperature storage system capable of carrying storage objects to a full capacity on a tray and of reliably transferring storage objects without the necessity for a camera to check the positions of a rack or storage objects. The low-temperature storage system includes a storage area inside a low-temperature storage chamber for storing storage objects, and a picking area where a positioning device is disposed to allow storage objects to be carried in and out. The positioning device includes a rack fixing unit that fixes a rack, a tray fixing unit, and a drive mechanism. The rack fixing unit includes a rack pressing member that presses the rack, and a rack motion restricting member that restricts movements of the rack. The tray fixing unit includes a tray pressing member that presses the tray, and a tray motion restricting member that restricts movements of the tray.