An uninterruptible power supply device comprising: a converter configured to convert AC power from an AC power supply into DC power and output the DC power to a DC bus; an inverter configured to convert the DC power received from the DC bus into AC power and supply the AC power to a load; a first bidirectional chopper configured to transmit and receive DC power between the DC bus and a first power storage device; a second bidirectional chopper configured to transmit and receive DC power between the DC bus and a second power storage device; a first controller configured to control the first bidirectional chopper such that a current flows from the DC bus to the first power storage device when the AC power is supplied normally from the AC power supply, and control the first bidirectional chopper such that a current flows from the first power storage device to the DC bus when the AC power is not supplied normally from the AC power supply; and a second controller configured to perform a first mode, in the first mode, the second controller being configured to control the second bidirectional chopper such that a current flows from the DC bus to the second power storage device when the load is performing a regenerative operation, and control the second bidirectional chopper such that a current flows from the second power storage device to the DC bus when the load is performing a power running operation, characterized in that the second controller is configured to perform the first mode when a time for which the load is not performing the regenerative operation is shorter than a predetermined time, and switch from the first mode to a second mode when the regenerative operation of the load is not performed even after the lapse of the predetermined time, indicating that the connected load is not configured to perform a regenerative operation; wherein in the second mode, the second controller is configured to control the second bidirectional chopper such that the current flows from the DC bus to the second power storage device when the AC power is supplied normally from the AC power supply, and control the second bidirectional chopper such that the current flows from the second power storage device to the DC bus when the AC power is not supplied normally from the AC power supply. a converter configured to convert AC power from an AC power supply into DC power and output the DC power to a DC bus; an inverter configured to convert the DC power received from the DC bus into AC power and supply the AC power to a load; a first bidirectional chopper configured to transmit and receive DC power between the DC bus and a first power storage device; a second bidirectional chopper configured to transmit and receive DC power between the DC bus and a second power storage device; a first controller configured to control the first bidirectional chopper such that a current flows from the DC bus to the first power storage device when the AC power is supplied normally from the AC power supply, and control the first bidirectional chopper such that a current flows from the first power storage device to the DC bus when the AC power is not supplied normally from the AC power supply; and a second controller configured to perform a first mode, in the first mode, the second controller being configured to control the second bidirectional chopper such that a current flows from the DC bus to the second power storage device when the load is performing a regenerative operation, and control the second bidirectional chopper such that a current flows from the second power storage device to the DC bus when the load is performing a power running operation, characterized in that the second controller is configured to perform the first mode when a time for which the load is not performing the regenerative operation is shorter than a predetermined time, and switch from the first mode to a second mode when the regenerative operation of the load is not performed even after the lapse of the predetermined time, indicating that the connected load is not configured to perform a regenerative operation; wherein in the second mode, the second controller is configured to control the second bidirectional chopper such that the current flows from the DC bus to the second power storage device when the AC power is supplied normally from the AC power supply, and control the second bidirectional chopper such that the current flows from the second power storage device to the DC bus when the AC power is not supplied normally from the AC power supply.