A crystal oscillator with a configuration that allows for reduction of power consumption includes a crystal element, a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a ninth transistor, a crystal element. The crystal element includes a first terminal coupled to a control terminal of the seventh transistor and a second terminal coupled to a first terminal of the seventh transistor. The second transistor includes a control terminal coupled to an output terminal of the crystal oscillator and a first terminal of the ninth transistor.