A dielectric device includes a dielectric substrate that includes at least one resonator unit. An external conductor film covers most of the outer surface of the dielectric substrate, except one end surface. The at least one resonator unit includes a first hole and a second hole. The first hole is provided in the dielectric substrate, extending from the end surface to an opposite surface, being open at the end surface and the opposite surface, and having a first internal conductor inside thereof. The second hole is provided in the dielectric substrate at a predetermined distance from the first hole, extends from the end surface toward the opposite surface, being open at the end surface, closed at the opposite surface, and having a second internal conductor inside thereof. The second internal conductor is connected to the first internal conductor at the end surface.