An output buffer circuit comprises a pair of first and second output MOS transistors coupled between a power supply line and a ground line; a booster circuit for boosting the power supply voltage up to a predetermined high voltage higher than a power supply voltage; a complementary MOS circuit comprising a pair of n-channel and p-channel MOS transistors connected in series between an output side of the booster circuit and the ground line; and a level shifter circuit having a first terminal coupled to an output side of a first logic gate for receiving logic signals from the first logic gate, a second terminal coupled to the gates of the n-channel and p-channel MOS transistors of the complementary MOS circuit and a third terminal coupled to the output side of the booster circuit for receiving the predetermined high voltage from the booster circuit, the level shifter circuit performing to shift the logic signal of the logic gate up to at least almost the same level as the predetermined high voltage to supply a shifted up signal to the gates of the n-channel and p-channel MOS transistors of the complementary MOS circuit.