A cell voltage equalizer for a multi-cell battery pack which includes a plurality of cells (BT-1...BT-11) connected together in series and outputs a desired voltage, the cell voltage equalizer configured to equalize output voltages from the respective cells (BT-1...BT-11), the cell voltage equalizer comprising: a voltage measuring device configured to measure the output voltages from the respective cells (BT-1...BT-11); a discharge device, provided to each of the cells (BT-1...BT-11), configured to discharge the output voltages from the respective cells (BT-1...BT-11) by causing electric currents to flow between positive electrodes and negative electrodes of the cells (BT-1...BT-11); a state-of-charge measuring device configured to find a state of charge of the multi-cell battery pack on the basis of at least an output voltage from a cell out of the output voltages from the cells (BT-1...BT-11) which are measured by the voltage measuring device, and judging whether or not the state of charge is a predetermined level not greater than a preset first threshold value; a differential value arithmetic device configured to find differential values by subtracting a preset predetermined baseline voltage from the output voltages from the cells (BT-1...BT-11) measured by the voltage measuring device; and an equalization controlling device configured to equalize the output voltages from the respective cells (BT-1...BT-11) if there exists a cell whose differential value found by the differential value arithmetic device is not less than a first voltage threshold value, by making the cell discharged by the discharge device which is provided to the cell, wherein in a case where the state of charge measured by the state-of-charge measuring device is not the predetermined level, the equalization controlling device performs the equalizing process on the cells (BT-1...BT-11) on the condition that a preset first waiting time has passed since the previous equalizing process, and in a case where the state of charge is the predetermined level, the equalization controlling device performs the equalizing process on the cells (BT-1...BT-11) on the condition that a second waiting time, which is shorter than the first waiting time, has passed since the previous equalizing process. a voltage measuring device configured to measure the output voltages from the respective cells (BT-1...BT-11); a discharge device, provided to each of the cells (BT-1...BT-11), configured to discharge the output voltages from the respective cells (BT-1...BT-11) by causing electric currents to flow between positive electrodes and negative electrodes of the cells (BT-1...BT-11); a state-of-charge measuring device configured to find a state of charge of the multi-cell battery pack on the basis of at least an output voltage from a cell out of the output voltages from the cells (BT-1...BT-11) which are measured by the voltage measuring device, and judging whether or not the state of charge is a predetermined level not greater than a preset first threshold value; a differential value arithmetic device configured to find differential values by subtracting a preset predetermined baseline voltage from the output voltages from the cells (BT-1...BT-11) measured by the voltage measuring device; and an equalization controlling device configured to equalize the output voltages from the respective cells (BT-1...BT-11) if there exists a cell whose differential value found by the differential value arithmetic device is not less than a first voltage threshold value, by making the cell discharged by the discharge device which is provided to the cell, wherein in a case where the state of charge measured by the state-of-charge measuring device is not the predetermined level, the equalization controlling device performs the equalizing process on the cells (BT-1...BT-11) on the condition that a preset first waiting time has passed since the previous equalizing process, and in a case where the state of charge is the predetermined level, the equalization controlling device performs the equalizing process on the cells (BT-1...BT-11) on the condition that a second waiting time, which is shorter than the first waiting time, has passed since the previous equalizing process.