This paper proposes a novel magnetic antenna with dual circular polarizations. Two circular loop antennas are arranged in spatially mutual orthogonality. The differential branch-line coupler, which can generate a set of four quadrature phases of 0, 90, 180, and 270 degrees with equal amplitude, is designed and used to excite the magnetic loop antenna. Right-handed or left-handed circular polarization (RHCP or LHCP) is determined by the sign of relative phase difference. The numerical results of the scattering parameters and the radiation patterns are presented.