An internal voltage generator capable of reducing the variation width in the level of an internal voltage VPP, by performing charge pumping only a predetermined number of times in a period where an oscillator driving signal is at a logic HIGH level, and then stopping the charge pumping operation. The oscillator controller generates an oscillation control signal for stopping an oscillation operation of a ring oscillator by using an output signal of a level detector and an output signal of the ring oscillator. The ring oscillator does not generate an oscillation signal at a predetermined time point where an output signal of the level detector is at a HIGH level in response to the oscillation control signal. The charge pump circuit generates an internal voltage by performing a charge pumping operation only predetermined times in response to the oscillation signal, and then stopping the charge pumping operation.