The areal power information center (5) collects, via the communications line (20), the system information on the power flow and the voltage in the areal power transmission/distribution system (10). Also, the center (5) collects the customer information on the consumed-power amounts by the respective customers (3a, 3b, 4), and on the generated-electricity amounts by the customers (3b). Moreover, the center (5) collects the wheeling information on a wheeling request for requesting a power transmission from one customer (3b) to another customer (3b). Furthermore, based on the respective information collected, the center (5) controls the reactive power from the areal-power-transmission/distribution-system voltage regulator (17), and the output-power from the electric generators (40). This control allows the center (5) to suppress a congestion of the power flow in the areal power transmission/distribution system (10).