Provided is a high voltage generator including a level detector for selecting one of a plurality of voltage sources in accordance with an option control signal and comparing the selected voltage source with a Vpp voltage; a first oscillator for generating a plurality of pulse signals having different periods, the first oscillator being operated in accordance with the option control signal; a second oscillator for generating pulse signals, the second oscillator operated in accordance with the option control signal; a first charge pump for generating the Vpp voltage by performing a pumping operation in accordance with an output of the first oscillator, the first charge pump being enabled in accordance with the option control signal; and a second charge pump for generating the Vpp voltage by performing a pumping operation in accordance with an output of the second oscillator, the second charge pump being enabled in accordance with the option control signal.