An atomic oscillator includes a gas cell into which alkali metal atoms are sealed, a light emitting portion that emits excitation light including a pair of resonance light beams for resonating the alkali metal atoms toward the alkali metal atoms, a coil that is provided to surround an outer circumference of the gas cell with an axis of the excitation light as an axial direction, and a shield case that stores at least the gas cell and the coil and contains a metal material, in which the shield case is constituted by a plurality of tabular portions, and, among the plurality of tabular portions, a main surface of one of two adjacent tabular portions faces a side surface of the other tabular portion.