PURPOSE: To lower a voltage and to miniaturize a frequency variable type quartz oscillation circuit.

CONSTITUTION: The serial connection of a first fixed capacitor 13 and a (p) channel MOS resistor 15 is provided between the output terminal of an oscillation inverter 3 and a power source, a second fixed capacitor 17 is provided between the input terminal of the oscillation inverter 3 and the power source and the gate of the (p) channel MOS resistor 15 is connected to an external input terminal 19. Thus, the adjustment width of a frequency is widened even with a low voltage below 3V and this quartz oscillation circuit is constituted of only elements capable of being easily incorporated in a semiconductor integrated circuit for all the parts except a quartz oscillator.