A PLL circuit according to an exemplary aspect of the present invention includes: a PFD that detects a phase difference between two clock signals; an LPF that outputs a voltage based on a detection result of the PFD; a VCO that controls a frequency of a VCO output clock output based on the voltage; a frequency divider that divides a frequency of the VCO output clock and outputs an output clock; and an automatic adjustment circuit that adjusts a frequency division ratio of the frequency divider based on the voltage. The automatic adjustment circuit includes a comparison circuit that outputs a control signal for controlling the frequency divider and a control signal for controlling the reference voltage. This circuit configuration makes it possible to control an oscillation frequency of a PLL circuit with accuracy and stability.