Abstract: Disclosed is an apparatus for compensating passband flatness according to the present invention. The apparatus for compensating passband flatness for a mobile communication repeater to compensate passband flatness of band passed input signals comprises: a circuit for compensating passband flatness that includes a varactor diode formed to be connected to an inductance element to correct micro resonance frequencies for passbands of input signals according to voltages applied from the outside; and a controller that controls voltages input to the circuit for compensating passband flatness and varies the voltages applied to the varactor diode of the circuit for compensating passband flatness based on preset voltage values applied to the varactor diode so that passband flatness characteristics are compensated according to the corresponding frequency bands.