A voltage equalizer includes: first, second, and third junction terminals respectively connected to a positive electrode of a first battery module, a positive electrode of a second battery module, and negative electrodes of the first and second battery modules; an equalizer circuit connected between the first and second junction terminals, and the equalizer forming a current path between the first and second junction terminals; a first indicator having a first displaying state that changes according to a voltage difference between the first and second junction terminals; a first comparator for outputting a first output voltage according to an input voltage that is input in proportion to a voltage between the first and third junction terminals; and a second indicator having a second displaying state that changes according to the first output voltage of the first comparator.