A quantum interference device (atomic oscillator) includes a light source unit as a coherent light source, a unit that superimposes microwave on the light source unit to generate a side band, an atom cell in which an alkali metal gas is enclosed, and a light receiving unit that detects light transmitted through the atom cell, wherein the light source unit is a surface-emitting laser that outputs a zero-order mode light and a plurality of higher-order mode lights, and a mode filter that cuts the higher-order mode lights is placed between the light source unit and the atom cell.