A safety device for stairway elevator systems (10) used for transporting apparatus and goods, especially wheelchairs (9) with persons who are unable to walk. The device is characterized in that the stairway elevator (10) or wheelchair (9) is fitted with a mounting device (20) equipped with a rotation pin (21). A support bracket (30) is mounted on the rotation pin (21) and a braking and blocking device (40) is attached to both the support bracket (30) and mounting device (20). A sensor (70) controls the braking and blocking device (40) in such a way that it blocks the support bracket (30) as soon as the stairway elevator (10) is at risk of tipping over and down the stairs (1) and releases the support bracket (30) when the stairway elevator (10) is placed at a correct angle to the stairs(1).