Using the hypercharge-charge representation, leptonic decays of elementary particles are considered under the symmetry of the group B2. Baryons and mesons are assigned to the 4-dimensional representations of the group B2, then the 10-dimensional regular representation just contains all |△S|≤1 and |△Q|≤l baryonic currents or mesonic currents. Assumming that the weak interaction is mediated by intermediate bosons, and inserting them into the 10-dimensional representation of B2, we have calculated various leptonic decay rates of strange particles which involve both △S = + △Q and △S = - △Q processes. The results here obtained are not in contradiction to present experimental data.