A power supply apparatus capable of reducing power consumption and a liquid crystal display including the power supply apparatus includes a first DC-AC converting unit enabled by a driving signal to convert a DC voltage into a first AC voltage, increase the first AC voltage, and supply the increased first AC voltage as a first power supply voltage; a switching unit which selectively transmits the driving signal in response to a selection signal; and a second DC-AC converting unit enabled by the driving signal selectively transmitted by the switching unit to convert the DC voltage into a second AC voltage, increase the second AC voltage, and supply the increased second AC voltage as a second power supply voltage.