An internal voltage generator and a method of generating an internal voltage are disclosed. The internal voltage generator includes: a charge pumping block configured to perform charge pumping base on a period pulse signal to generate an internal voltage, and output the generated internal voltage to an interval voltage terminal; a voltage detection block configured to detect the voltage level of the internal voltage terminal; a driving voltage supply block configured to supply a first power supply voltage or a second power supply voltage having a higher voltage level than the first power supply voltage as a driving voltage, depending on the detection result of the voltage detection block; and a period pulse generation block configured to drive the period pulse signal to the is driving voltage supplied from the driving voltage supply block. The period pulse signal driven by the second power supply voltage has a longer pulsing period than the period pulse signal driven by the first power supply voltage.