A multiphase converter controller with current balance, configured to control a plural converting circuit to commonly supply an output voltage, is disclosed. The multiphase converter controller comprises a feedback circuit, a fixed on-time circuit, and a multiphase logical circuit. The feedback circuit detects the output voltage to generate a feedback control signal. The fixed on-time circuit generates an on-time signal according to the feedback control signal, and a pulse width of the on-time signal is determined according to a single timer. The multiphase logical circuit chooses a corresponding converting circuit, generates a phase signal according to a sequence of the feedback control signal and controls the corresponding converting circuit according to the on-time signal. Wherein, the fixed on-time circuit determines a correction value according to currents of the plural converting circuit and the phase signal, so as to correct the pulse width of the on-time signal.