A network managing device for handling a data flow comprises a topology generating module, for generating a topology of at least one device of a network, and for determining at least one intelligent electric device (IED) of the at least one device according to the topology; a transmitting module, coupled to the topology generating module, for transmitting a request to a reception-transmission device, wherein the request is for requesting a substation information associated with the at least one IED; a receiving module, coupled to the transmitting module, for receiving the substation information from the reception-transmission device; a shortest path generating module, coupled to the receiving module, for generating a first shortest path of the at least one IED according to the substation information; and a data flow processing module, coupled to the shortest path generating module, for generating a data flow according to the first shortest path.