A power storage device includes: power storage units each including at least one battery, the power storage units being connected in series; cell balance units connected in parallel to the respective power storage units via switches; and a control unit that performs control to charge the power storage units with a first constant current value, and, when the power storage unit having the highest voltage among the power storage units reaches a first potential, connect the corresponding one of the cell balance units to the power storage unit having the highest voltage, and switch the charging current to a second constant current value that is smaller than the first constant current value.