An uninterruptible power supply system, including: a plurality of uninterruptible power supply devices which are connected in parallel with respect to a load, and switch between power supplies supplying power to the load depending on states of the power supplies; a control unit controlling an operation of switching between the power supplies by the uninterruptible power supply devices; a storage battery connected to the plurality of uninterruptible power supply devices in common; a converter converting AC power; a contactor switching between the DC power converted by the converter and DC power input from the storage battery; and an inverter inverting the DC power and supplying the power to the load. The control unit deactivates the inverter which does not contribute to supplying a power amount required for the load, of a plurality of inverters.