A belt buckle is provided with a waist belt outlet slot (1) for connecting with a waist belt beginning (6) and at least one inlet retainer (5) engaging in openings of the belt at the opposite waist belt inlet slot (2).As a result of the design of the central section of the belt buckle as an essentially flat element (3), which permits deflection toward the waist belt, which reaches in the section of the, or of each inlet retainer (5) at least their height, can, in spite of a simple design, prevent an opening that is against the will of the carrier.