A semiconductor integrated circuit device includes: first and second transistors provided between a first power source and an output terminal; a step-down circuit that generates a second power source from the first power source; a power source switch circuit that outputs, as a fourth power source, a higher one of potentials of the second power source and a third power source; and a level shifter circuit that transits between the first power source and a fourth power source. The first transistor has a gate connected to an output of the level shifter circuit; the second transistor has a gate connected to the fourth power source.