An atomic oscillator including an oscillator that outputs an oscillation signal, a light emitter to which a signal based on the oscillation signal is inputted, an atomic cell, a light receiver that detects the light passing through the atomic cell and outputs a detection signal, a first temperature controller, and a control circuit, and the control circuit has a first mode including the process of operating the light emitter and the first temperature controller and the process of causing the oscillator to output the oscillation signal, a second mode including the process of causing the light emitter and the first temperature controller to stop operating and the process of causing the oscillator to stop outputting the oscillation signal, and a third mode including the process of causing the light emitter to stop operating, the process of operating the first temperature controller, and the process of causing the oscillator to stop outputting the oscillation signal.