In an uninterruptible power supply device for supplying DC power to a load, a control device is configured such that, when the load is performing power running operation, the control device turns on a second switch to supply DC power from a diode rectifier to the load, turns off a first switch, and controls a converter to suppress a harmonic current contained in an AC current flowing from an AC power supply to the diode rectifier, and when the load is performing regenerative operation, the control device turns off the second switch, turns on the first switch, and controls the converter to convert regenerative power generated by the load into AC power.