A grayscale voltage generating circuit includes a first constant-voltage source for generating a high potential; a second constant-voltage source for generating a low potential; γ resistor connected between outputs of the first and second constant-voltage sources; a difference voltage detecting circuit for detecting a difference voltage across the γ resistor; and a voltage-to-current converting circuit for converting the difference voltage to a current by a resistor and outputting the current as a source current and a sink current. The source current output and sink current output of the voltage-to-current converting circuit are connected to the high and low potential sides, respectively, of the γ resistor.