Abstract: An oscillation circuit capable of outputting an oscillation signal of constant frequency free from the influence of source voltage, temperature, and nonuniformity and fluctuation in inverter threshold voltage. An inverter inverts a voltage applied to one end of a capacitive element and outputs the inverted voltage to transistors and an inverter. A constant voltage source outputs a constant voltage free from the influence of source voltage and temperature. The transistors connect the other end of the capacitive element to the constant voltage source or ground in accordance with the voltage output from the first-mentioned inverter. A constant current source causes a constant current free from the influence of the source voltage and temperature to flow into or out of the one end of the capacitive element in accordance with the voltage from the second-mentioned inverter connected to the first-mentioned inverter.