With an offset circuit including transistors of the same conductivity type, offset of an input signal is performed. Then, the input signal after the offset is supplied to a logic circuit including transistors of the same conductivity type as that of the offset circuit, thereby H and L levels of the input signal can be shifted at the same time. Further, since the offset circuit and the logic circuit are formed using the transistors of the same conductivity type, a display device can be manufactured at a low cost.