An atomic oscillator includes an atom cell having an internal space in which alkali metal is encapsulated, a first light source section for making a resonance light pair, which is circularly polarized in the same direction as each other and resonates the alkali metal, enter the internal space using light from a first light source, a second light source for making adjustment light, which is circularly polarized in a rotational direction opposite to the direction of the resonance light pair and resonates the alkali metal, enter the internal space from the same side as the resonance light pair using light from a second light source, and an aperture member disposed between the internal space, and the first light source and the second light source.