Disclosed is a high voltage generator comprising: a first voltage level detector for detecting a voltage level of the high voltage; a second voltage level detector for detecting difference between the high voltage and a power supply voltage; a high voltage pump for performing a pumping operation to generate a high voltage when one of output signals of the first voltage level detector and the second voltage level detector is enabled; and a controller for receiving the output signal of the second voltage level detector, and for connecting a terminal through which the high voltage is output with the power supply voltage when the high voltage is lower than the power supply voltage.