A negative voltage supply device includes a negative voltage detector and a negative voltage pumping unit. The negative voltage pumping unit pumps a negative voltage in response to a detection signal. The negative voltage detector detects a level of a negative voltage by using a first element and a second element, which are different in the degree of change in their respective resistance values depending on the temperature, and outputs the detection signal. The detection signal informs the negative voltage pumping unit that pumping of the negative voltage is no longer needed.