The present invention relates to a power management system (PMS) for multiple energy storage systems (ESS) that is for integrated management of the system having multiple ESS for controlling a frequency and having a hierarchical control structure. The PMS for ESS comprises: a plurality of ESS; a local management system (LMS) for managing one or more ESS of the plurality of ESS for each local unit; an ESS Controller (ESSC) for general management of the LMS, judging a state of the LMS and determining an output value of one or more ESS in the LMS, and transmitting the determined output value to the respective ESS; and a PMS for general management of the entire system comprising the plurality of ESS, the LMS and the ESSC, judging the state of the entire system and participating in a power grid frequency control market through a grid operator contract, controlling the output of the LMS, and adjusting a control parameter for output control.