Abstract: Buckle of a seat belt for a motor vehicle comprising a male part and a female part characterized in that it comprises electric contacts carried by two tongues (30, 35), a first tongue (30) comprising a V-shaped section with two branches (31, 32), one of which constitutes an electric contact and a cambered end (34), the convex sections of these two sections facing opposite the second tongue (35) which has a V-shaped section with branches (36, 37), one of which constitutes an electric contact and is designed to bear against the electric contact of the first tongue (30), the cambered section (34) being designed to cooperate with a bar (10) to control the opening of the electric contacts moved by the introduction of the male part of the buckle.