A phase adjusting circuit is provided that can highly precisely adjust frequencies throughout the entire frequency range to be dealt with. A PLL circuit includes: a reference-signal input terminal from which a reference signal is input; a feedback-signal input terminal from which a feedback signal is input; and an output terminal from which an output signal based on a phase difference between the reference signal and the feedback signal is output. A filter circuit is connected to the reference-signal input terminal and the output terminal, and causes a phase of the reference signal to be delayed when the oscillation frequency of an inverter circuit including the PLL circuit falls in a high range. A delay circuit is connected to the output terminal, and causes the output signal to be delayed when the oscillation frequency of the inverter circuit falls in a low range lower than the high range.