An uninterruptible power supply device includes: a converter that converts AC power supplied from an AC power supply into DC power and outputs the DC power to a first power supply node; a first bidirectional chopper that outputs DC power in a lead storage device to the first power supply node when the AC power supply has a power failure; a diode connected between the first power supply node and a second power supply node; a second bidirectional chopper that supplies and receives DC power between the second power supply node and a lithium ion battery; and a controller that controls the second bidirectional chopper to charge the lithium ion battery during regenerative operation of a load and to discharge the lithium ion battery during power running operation of the load.