A frequency stabilization device includes a first radiating element, a second radiating element, a feeding circuit connected to the first and second radiating elements, and a frequency stabilization circuit disposed between the feeding circuit and the first radiating element. The frequency stabilization circuit includes a primary-side series circuit connected to the feeding circuit and a secondary-side series circuit coupled to the primary-side series circuit via an electric field or a magnetic field. A first inductance element and a second inductance element are connected in series to each other, and a third inductance element and a fourth inductance element are connected in series to each other. The first and third inductance elements are coupled to each other, and the second and fourth inductance elements are coupled to each other.