A storage battery system connected to a power system includes: a storage battery; a BMU which monitors a state of the storage battery; a PCS which converts AC power of the power system into DC power to charge the storage battery with the DC power and converts DC power of the storage battery into AC power to discharge the AC power to the power system; and a control device. The control device receives a charge/discharge request from an EMS and storage battery information supplied from the BMU and controls the PCS based on the charge/discharge request and the storage battery information. The control device includes a charge/discharge command unit which calculates chargeable/dischargeable electric power based on the storage battery information and determines a charge/discharge command to the PCS based on the charge/discharge request by using the chargeable/dischargeable electric power as a constraint condition.