the present invention provides a voltage generating circuit and a control method thereof which is capable of preventing an increase in the occupied area and suitable for raising the voltage of the power supply in a wide range . this voltage generating circuit comprises a first charge pump unit to which a first clock signal is inputted , wherein the first charge pump unit generates a voltage by pumping a voltage of a first external power supply in stages by a first voltage , a voltage selector that selects the voltage generated by the first charge pump unit or a voltage of a second external power supply in accordance with a voltage selection command signal , a level converter that converts a voltage level of the first clock signal into a second voltage level , and a second charge pump unit to which the second clock signal that has been converted by the level converter is inputted , wherein the second charge pump unit and that generates a voltage and by pumping the selected voltage or the voltage of the second external power supply .