To provide a luminance adjusting apparatus making it possible to narrow the output dynamic range of a picture signal processing section and decreasing the cost of a horizontal driver. The following are arranged: a variable gamma correction circuit (12) for synchronously changing an inflection point of a gamma correction curve and a common voltage generated by a common voltage control circuit (7) by the fact that a luminance adjusting dial is adjusted, a timing signal processing circuit (3) for generating a timing pulse, a picture signal processing circuit (5) for processing a picture signal, a horizontal driver, a common voltage generation circuit (7) for generating a common voltage, a vertical driver (8), and a common driver (9). A picture signal is inputted to the variable gamma correction circuit (12) from a signal source and the inflection point of the gamma correction curve and the common voltage generated by the common voltage control circuit (7) are synchronously changed by manually adjusting the luminance adjusting dial.