A novel magnitude and phase indirect correction technique for active baluns was proposed to solve the amplitude and phase mismatch between outputs at millimeter wave frequency. With this technique, the input gain and phase errors are equally distributed and recombined by common emitter-common base structure. In the process of distribution and combination, the unknown variable errors between the input signals were transformed into the inherent errors caused by the correction circuits so as to restrict and indirectly correct the input gain and phase errors, resulting in a new ideal differential output signal. The mathematical model and derived formulas confirmed the feasibility of the technique in ideal conditions and the simulation demonstrated the effectiveness of the circuit and validated the theoretical analysis. The simulation results show that the 3 dB bandwidth of the correction circuit was 96-113 GHz and the maximum power gain was 12.7 dB. The differential outputs had gain error less than 0.3 dB and phase error less than 5.3° when the inputs had gain error from 0 dB to 10 dB and phase error from 10° to 110° at 105 GHz. The dc power consumption was 54 mW.