An arrangement for monitoring the leak-tightness of an evacuated space which is hermetically closed, leak-tight, by means of at least one metallic wall is specified. A device which is connected to the evacuated space indicates an inadmissible pressure rise in the evacuated space caused by a leak in the wall. The device includes a metallic bellows, which is hermetically connected, leak-tight, to the evacuated space, and an electrical proximity switch to which an evaluation unit is connected. The proximity switch (7) is mounted, in the direction of movement of the bellows (5), at a distance from the end face of the latter, the size of which is varied as a function of the respective axial length of the bellows (5). A tube (9) connected fixedly to the wall (2) is mounted around the bellows (5), so as to maintain an air gap, surrounds the bellows (5) in a moisture-tight manner and is longer than the bellows (5) in its longest initial position corresponding to the expanded state. The proximity switch (7) projects into the tube (9) so as to be sealed off with respect to the latter.