A voltage equalization device for a power storage device which includes a plurality of battery packs and a plurality of power converters and in which the plurality of battery packs are connected in parallel via each of the plurality of power converters, the plurality of power converters being respectively associated with the plurality of battery packs and performing voltage adjustment for the respectively associated battery packs, the voltage equalization device comprising: a deciding means arranged to obtain battery-pack information which is information regarding states of charge/discharge of each of the plurality of battery packs and for deciding, for each of the plurality of battery packs, whether or not the difference between the value indicated by the obtained battery-pack information and a previously-determined value as a reference value of the battery-pack information is equal to or more than a predetermined threshold; a plurality of bypass impedance elements that are respectively connected in parallel with the plurality of battery packs; a plurality of switching elements that are respectively associated with the plurality of battery packs and that are respectively connected in series with the plurality of bypass elements; a first voltage-adjusting means arranged to cause each of the plurality of power converters to perform voltage adjustment; and a second voltage-adjusting means arranged to control each of the plurality of switching elements, wherein the second voltage-adjusting means is arranged to turn on one of the plurality of switching elements associated with one of the plurality of battery packs for which the deciding means has decided that the difference is equal to or more than the predetermined threshold; the first voltage-adjusting means is arranged to cause the power converter associated with the one of the plurality of battery packs to perform voltage adjustment; the second voltage-adjusting means is arranged to turn off another one of the plurality of switching elements associated with another one of the plurality of battery packs for which the deciding means has decided that the difference is less than the predetermined threshold; and the first voltage-adjusting means is arranged to cause the power converter associated with the another one of the plurality of battery pack to perform voltage adjustment. a deciding means arranged to obtain battery-pack information which is information regarding states of charge/discharge of each of the plurality of battery packs and for deciding, for each of the plurality of battery packs, whether or not the difference between the value indicated by the obtained battery-pack information and a previously-determined value as a reference value of the battery-pack information is equal to or more than a predetermined threshold; a plurality of bypass impedance elements that are respectively connected in parallel with the plurality of battery packs; a plurality of switching elements that are respectively associated with the plurality of battery packs and that are respectively connected in series with the plurality of bypass elements; a first voltage-adjusting means arranged to cause each of the plurality of power converters to perform voltage adjustment; and a second voltage-adjusting means arranged to control each of the plurality of switching elements, wherein the second voltage-adjusting means is arranged to turn on one of the plurality of switching elements associated with one of the plurality of battery packs for which the deciding means has decided that the difference is equal to or more than the predetermined threshold; the first voltage-adjusting means is arranged to cause the power converter associated with the one of the plurality of battery packs to perform voltage adjustment; the second voltage-adjusting means is arranged to turn off another one of the plurality of switching elements associated with another one of the plurality of battery packs for which the deciding means has decided that the difference is less than the predetermined threshold; and the first voltage-adjusting means is arranged to cause the power converter associated with the another one of the plurality of battery pack to perform voltage adjustment.