An antenna device is provided, including a first substrate, a first conductive element, a second substrate, a second conductive element, and an insulating layer. The first conductive element is disposed on the first substrate to define, on the first substrate, a recessed region adjacent to the first conductive element. The second substrate faces the first substrate. The second conductive element is disposed on the second substrate and located between the first substrate and the second substrate. The insulating layer is disposed between the first substrate and the second substrate. In a top view of the antenna device, the second conductive element overlaps the first conductive element and the recessed region, and the insulating layer at least partially overlaps the recessed region.