Provided is a complementary metal oxide semiconductor (CMOS) input buffer circuit that is capable of lower voltage operation with lower current consumption. The CMOS input buffer circuit includes: a depletion type NMOS transistor including a drain connected to a power supply terminal (VDD), and a gate connected to an output terminal; a PMOS transistor including a source connected to a source of the depletion type NMOS transistor, a drain connected to the output terminal, and a gate connected to an input terminal; and an NMOS transistor including a source connected to a reference terminal (GND), a gate connected to the input terminal, and a drain connected to the output terminal.