An atomic oscillator using a quantum interference effect, includes: a first light source unit emitting first light which includes a resonant light pair having two different wavelengths; a gas cell sealed with alkali metal atoms; a first light detection unit detecting a light intensity of the first light which is transmitted through the gas cell; a second light source unit emitting second light towards the gas cell; and a control unit changing a light intensity of the second light which is emitted from the second light source unit to compensate a change in the light intensity detected by the first light detection unit.