Power supply device capable of equalizing electrical properties of batteries

A transformer 21 includes charging secondary winding lines 24 that can charge batteries 11 composing a corresponding cell block, and a discharging secondary winding line 26 that can discharge the corresponding cell block. Each of the charging secondary winding lines 24 is connected to corresponding one of the batteries 11 through corresponding one of secondary-side rectification output circuits 25 and corresponding one of output control switches 22. The discharging secondary winding line 26 is connected to a block discharging circuit through a block discharging switch 28. A switching control circuit 23 controls the block discharging switch 28. The switching control circuit 23 controls the output control switches 22 so that the electrical properties of the batteries 11 in the cell block are equalized. In addition, the switching control circuits 23 control the block discharging switches 28 so that the electrical properties of the batteries among the cell blocks are equalized.