Disclosed herein is a power supply device capable of correcting power factor. The power supply device includes a rectification circuit, a first constant current circuit, a capacitor, and a second constant current circuit. The rectification circuit rectifies input Alternating Current (AC) voltage. The first constant current circuit is connected in series to a load. The capacitor is connected in parallel to the first constant current circuit and the load that are connected in series to each other. The second constant current circuit is disposed between the output of the rectification circuit and the capacitor.