An atomic oscillator includes an atom cell that accommodates an alkali metal atom, a container that accommodates the atom cell, a heating device that is disposed in the container and heats the atom cell, a substrate on which the container is disposed, and a positioning member that is disposed on the substrate and positions the container. The atom cell is pressed against the container toward the heating device. The heating device is pressed against the container toward the atom cell, and the container is in turn pressed against the positioning member.