A word line voltage generator that generates a word line voltage, which is selectively changed depending on a temperature, a flash memory device including the word line voltage generator, and a method of generating the word line voltage. The word line voltage generator includes a read voltage generator and a controller. The read voltage generator generates a read voltage or a verify voltage based on one of reference voltages in response to an enable control signal and supplies the read voltage or the verify voltage to one of a plurality of global word lines in response to a row decoding signal, during a read operation or a read operation for program verification, of the flash memory device. The controller generates one of the reference voltages in response to a read control signal or a verify control signal. When a temperature is varied, the read voltage generator changes the level of the read voltage or the verify voltage in reverse proportion to the temperature.