A device (1) for loading and unloading containers (2) into and out of an enclosure of an installation (3) for treating substances contained in containers (2). The device includes a support structure (17) and a third means (16, 19, 21) for moving a second means (14) to a position higher than the containers. The second means (14) acts as a stop during loading and as a pusher during unloading. The device includes an extendible platform (10), wherein the extendible platform unfurls from the support structure (17) and the third means comprise parts (16a 16b) that unwind from the support structure (17) to the interior of the enclosure. The device is completely automatic, fast, takes up little space and is easy to disassemble.