In order to reduce a circuit scale such as a brightness adjustment circuit or the number of pins in an IC chip, in the brightness adjustment circuit, a brightness adjusted video signal (internal video signal) output from an analog signal synthesis circuit or a D/A converter is input to one input terminal of a switch and a sample/hold circuit. The sample/hold circuit holds a voltage of a level in accordance with the pedestal level of the internal video signal at a timing in accordance with a sampling pulse in synchronization with the internal video signal. A clamp circuit clamps the pedestal level of an external video signal in accordance with a clamp pulse, using the voltage held by the sample/hold circuit as the reference voltage, and input it to the other input terminal. The output terminal of the switch is connected to an amplifier.