A high-accuracy clock signal is generated even when the settings of the clock frequency are changed or there is a variation in power supply, temperature, or the like. A frequency-voltage conversion circuit includes a switch portion including switches, electrostatic capacitive elements, and other switches. The electrostatic capacitive elements have different absolute capacitance values, and are provided so as to cover a frequency range intended by a designer. For example, based on 4-bit frequency adjustment control signals, the other switches select the electrostatic capacitive elements having the electrostatic capacitance values thereof each weighted with 2 to perform the switching of a frequency.