PURPOSE: To provide an energy charging/discharging apparatus in a simple structure with a flywheel for generating electric energy with good characteristics.

CONSTITUTION: An inductor element 13 joined with a flywheel 14 is connected to a local power line 3 with a bidirectional inverter 12 in between. When a power load unit 5 is under a given electric energy level set in accordance with output performance of a power supply, an output frequency is raised above a set value to rotate the inductor element 13 as a motor and store rotational energy in the flywheel 14. When the power load unit 5 is above the given energy level, the inverter 12 generates an output frequency lower than the set value to rotate the inductor element 13 as a generator at the same speed as the flywheel 14. In this case, the stored energy is converted from rotational energy to electric one, and the power is fed to the local power line 3 through the inverter 12.