The invention relates to a seat belt buckle for a seat belt comprising a casing, a locking member for a plug-in latch and an unlocking device (26) for releasing the unlocking member. The unlocking device (26) includes at least two unlocking surfaces (56, 60) which are independent of each other, wherein a predetermined force has to be applied to both unlocking surfaces (56, 60) for operating the unlocking device (26). The unlocking device (26) includes at least one fastening element (30) constituting an engaging connection with the casing, wherein the engaging connection prevents a movement of the unlocking device (26) in an unlocking direction of the locking member and the fastening element (30) has to be moved in a direction perpendicular to the unlocking direction for releasing the engaging connection.