A voltage equalizer includes voltage detectors that detect voltages of respective cells, switches, and a controller that repeatedly sets a lowest voltage among voltages detected by one of the voltage detectors to be a target voltage Vt1 or Vt2 in each of the battery packs, and that repeatedly turns on/off each of the switches such that the voltages of the cells other than the cell having the lowest voltage become the target voltage Vt1 or Vt2 in each of the battery packs, until the controller determines on the basis of the respective voltages detected by the voltage detectors that a cell balance control operation does not need to be performed.