An atomic oscillator includes a semiconductor laser, an atomic cell, a light receiving element, a first temperature control element, a heat transfer member, and a second temperature control element. The laser includes a resonator and an insulation layer disposed around the resonator. The resonator includes a first mirror layer, a second mirror layer, and an active layer disposed between the first mirror layer and the second mirror layer. The atomic cell is irradiated with light emitted from the semiconductor laser. In the atomic cell, an alkali metal atom is accommodated. The light receiving element detects intensity of light transmitted through the atomic cell and outputs a detection signal. The first temperature control element controls a temperature of the semiconductor laser. The heat transfer member is disposed in the insulation layer. The second temperature control element is controlled based on the detection signal and is connected to the heat transfer member.