Safety device for a vehicle seat which is fixed inside a vehicle including lateral guides. The safety device consists of at least one safety rail fixed in the vehicle, in the region between the guides, and comprises associated securing mechanisms which are connected to the vehicle seat, and co-operate with the safety rail in a non-contact manner for regular loads applied to the seat, and in the event of irregular, especially accident-related deformations and/or movements in the region of the vehicle seat, engage with the safety rail in such a way that they block further deformation/displacements. The securing mechanisms and the safety rail are embodied in such a way that, during the engagement, reaction forces which act in the direction of axes (X, Y, Z) of a standard vehicle co-ordinates system are applied in a distributed manner to at least two different engagement regions of the safety rail.