Abstract: A power supply controller is capable of regulating the amount of electrical power supplied to semiconductor fabrication facilities to amounts in accordance with processing conditions of each facility. The apparatus includes a plurality of process status detectors corresponding to the facilities, each status detector detecting an operation mode of each of the facilities and generating a mode detection signal. A plurality of unit controllers are provided, corresponding to the process status detectors, each unit controller generating a power control signal in response to the mode detection signal. A plurality of power supply units are provided, corresponding to the unit controllers, each power supply unit controlling and providing an amount of electrical power from the main power supply to the facilities in response to the power control signal corresponding the operation mode of each facility.