A power storage system includes multiple power storage devices, multiple power conversion devices, and a control device; the multiple power storage devices are capable of discharging and charging DC power; the multiple power conversion devices are connected to the multiple power storage devices and a bad, convert the DC power stored in the multiple power storage devices into power corresponding to the bad, supply the power to the bad based on the DC power stored in the multiple power storage devices, convert power of the load into DC power corresponding to the multiple power storage devices, and charge the multiple power storage devices based on the power of the load side; the control device controls a power conversion operation of the multiple power conversion devices. Accordingly, a power storage system and a control device are provided in which the power loss can be suppressed.