Oscillatory signal output circuitry includes a bias circuit generating a bias voltage, which is applied to an amplifier and an oscillatory circuit to generate an oscillatory signal. The oscillatory signal is capacitively coupled and level-shifted up by the bias voltage to produce output signals. The produced output signals are operatively applied to PMOS and NMOS transistors of an output part. When the voltages of the output signals decrease at the same time, the drain current of the NMOS transistor decreases to output a high level. When the voltages of the output signals increase at the same time, the drain current of the NMOS transistor increases to output a low level. Therefore, the output part attains its large gain, and is ensured to operate to develop the output signal. A variation in threshold voltage would cause the bias voltages to change accordingly, thus being ensured to output the output signal.