There is provided a display device capable of automatically controlling a luminance in response to a brightness of a surrounding. The display device has a gamma correction circuit for converting an image signal voltage into a drive voltage for gray scale display and a photosensor for controlling an input and output voltage characteristic of the gamma correction circuit in response to the brightness of the surrounding. In this case, the gamma correction circuit for converting the image signal voltage into the driver voltage for gray scale display is formed on a first substrate. The photosensor for controlling the input and output voltage characteristic of the gamma correction circuit in response to the brightness of the surrounding is formed on a second substrate. The second substrate is fixed to the first substrate.