A level shifter that accommodates lower driving voltage of a driver circuit and has a sufficient capability of converting the amplitude of an input signal even when the voltage amplitude of the input signal is low is provided. A level shifter utilizing a current mirror circuit 150 and a differential circuit 160 is used in a portion for converting the voltage amplitude of the signal. Since the potential difference of a signal input through transistors 105 and 106 to the differential circuit 120 is amplified and outputted, the voltage amplitude can be normally converted without influence of the threshold of a transistor even when the voltage amplitude of the input signal is low.