A voltage regulator includes an error amplifier configured to receive a first voltage through a first node as an operating voltage, to amplify a difference between a reference voltage and a feedback voltage, and to output an amplified voltage; a power transistor connected between a second node through which a second voltage is supplied and an output node of the voltage regulator; and a switch circuit configured to select a level of a gate voltage supplied to a gate of the power transistor and level of a body voltage supplied to a body of the power transistor in response to a first power sequence of the first voltage, a second power sequence of the second voltage, and an operation control signal.