Abstract: A closure device for a case of an antimagnetic material comprising a box part (1) and a sliding lid (5) requires neither in the lid nor in the box part break-throughs and offers high security against unauthorized opening of the case when at least one permanent magnetic locking pin (4a, 4b) is arranged slideable in the box part (1) at right angles to the plane of the lid (5), and is loaded in the direction of the lid (e.g. by means of a spring) so that the locking pin clasps behind a locking shoulder (6a, 6b; 66) configured on the inner side of the lid when closed. For opening the lid (5) an unlocking plate (7) may then be used comprising at the corresponding location a permanent magnet (8a, 8b) which is magnetized opposite the direction of magnetization of the locking pin (4a, 4b).