An auxiliary power supply device can include a first power storage unit, a first charging circuit to receive input power and charge the first power storage unit, a second power storage unit having lower power supply speed than the first power storage unit and longer power supply time than the first power storage unit, a second charge circuit to receive input power and charge the second power storage unit, and a switching unit to supply the stored power of the first power storage unit to external devices for a predetermined time when a sudden power-off occurs and supply stored power of the second power storage unit to the external devices after the predetermined time elapses.